I JUST finished fixing the exact same problem on a 5.7 Hemi. The lifter roller bearing had seized up locking up the bearing and then chewing away at the camshaft lobe, only mine was the #5 intake. Everything else identical. I didn't use a pressure tranducer, nor do I even have one so I will let others answer with a confident answer to your questions about the waveform, but judging by watching the rocker movement in your video and what I found on my repair, I believe what you are seeing is due to a change in the dwell timing of the valve opening and closing. The damaged lifter/camshaft lobe causes the valve to open late and close early. This has got to have an effect on the waveform in some manner. Great diagnostic on your part - you got to the problem much sooner than I did!
You're not going to believe this. I just watched "Pressure Waveform Acquisition & Analysis From the Inside Out". 96 minutes will answer pretty every question you ask yourself during this excellent video. I was blown away by the coincidence of seeing your presentation and then stumbling upon this one. I hope you watch it and like it.
MAP cranking WOT is atmospheric, MAP running at idle is about 1/3 of atmospheric therefore compression at idle will be about 1/3 of that cranking. You did footnote this in the video. Engine rpm will have little effect on compression pressure between 300 cranking and 600 idling. At 4000 peak torque rpm (where the engine breathes best (best volumetric efficiency) compression will be highest. There is an interaction between valve timing and air pulse flow that causes peak pressure at peak torque rpm. 34:00 It's not that the piston takes longer , it's the pressure is higher during combustion. The pressure left over before the exhaust valve opens is what causes the exhaust sound we love. Don't try snap throttle with your expensive pressure transducer. Think of the temperature fluctuations it goes through from compression let alone higher combustion temperature/pressure. It was a good experiment to try once because you could.
The reason you have high compression in cylinder one is that the intake valve is closed properly but it’s not opening properly thus the compression is high because we are measuring the pressure at the compression stroke witch requires both valves closed and the piston at tdc wich fits the requirements for a good compression when you unplugged the harness for the fuel nozzle the engine speed changed which indicate that the cylinder is working but with a little amount of air fuel mixture results in a poor power stroke because of the tiny opening of the intake valve detected by the crank position sensor signals the pcm to show the miss fire code Please correct me if I am wrong Thank you Matt for your efforts in teaching us a lot Looking forward for your next video
Great in depth video as always, very informative and easy to understand. If you look at the data on the compression test, you can see there is an anomaly on one of the cylinders - the test does show pretty much the same amount of compression throughout all the cylinders but on the pressure build up and let off there is something different. It isn't a smoking gun but there is a pattern in there
Ah yes I see it now, good observation. Didn’t think of it at the time as I just about ruled out compression on first glance. It does demonstrate that a standard gauge would not have detected any compression at all.
I like to have as many diagnostic "windows" open as possible. When one "window" can't verify the exact issue, I try a different window. The thing is, these "windows" are limited in what they will reveal to us. There is no "wrong" window, it's knowing the limitation of what that window can reveal. Great video Mr. Matt!!!!
Hey Paul great to see you. Yep I agree. I also like the idea what when you are on the right track, all the windows line up and support the same conclusion!
Just to correct you there, Matt - if we've learned anything at all from previous asshat interjections (and we really haven't), it's that the use of a broom handle is far preferable to a screwdriver for listening to an ailing engine. Works every time. 😂
The compression test is where you should start to diagnose most engines. Plus you get a look at the spark plugs at the same time. After that, do a leak down, 2 good important diagnostic tools. You can get a good idea of the mechanic, general mechanical condition of the engine.
Well the thing is you do the compression test on this engine and it shows normal. Even a leakdown test would show normal- the valves close! So now what do you do?
@@SchrodingersBox I’m wondering how you would get a good reading on compression in your cylinder and still be good ? I’m an aviation mechanic and when we see low compression the exhaust valve is almost always the culprit. I’m not saying that it can’t be other thing because it can be multiple things that add up but usually that’s the problem. Maybe I’m not understanding your statement. Are you asking about what to do if the compression is good and also a leak down test is good also ? Valve lash ,rings that sort of thing would be next if that’s what your asking. Sorry I’m not much help . Great Chanel by the way. I always like to check this guy out. Good info. Thanks for posting. Mike. ATL.
@@SchrodingersBox Move on and go down the list, at least you know the general mechanical condition is at least fair because you just crossed of a whole bunch possibility's off the list with those 2 tests
The mechanical condition is anything but fair though! It’s catastrophic!! The intake lift is barely measurable with a duration of less than 1/4 normal plus you can see the rocker arm is so loose the pushrod could be slipped right past it if you wanted to.
Mike the reason the compression still shows good is only because it’s being measured during cranking and at idle. In both cases you have minimal air intake anyway because the throttle is closed and in the case of idle there is also high engine vacuum. So the compression gauge doesn’t see anything different than normal- there is similar induction as usual plus the valves close upon compression stroke. The poor compression is going to only be present under load when the throttle is open and the intake vacuum is gone. The minimal valve lift and duration then becomes a major major issue as the cylinder cannot breathe due to being unable to draw air in.
Very good video you've clearly learned a lot over the last few years one of the reasons you've see compression is you are experiencing atmospheric pressure at 15 PSI ish trying to jump in the cylinder so a little inlet valve open will almost certainly fill the cylinder at cranking also you have valve overlap as you correctly said ,, and you will get some cylinder filling through the exhaust valve for the people watching this (controversially id go as far as saying in cylinder pressure testing is waste of time) you don't need a thousand dollar pressure transducer you can do all this testing with a piezo pressure pulse sensor around $50 US ( or make you own) I would also say when you're doing your cranking current analysis A general rule of thumb is three times battery amp specification ( not the battery that might have been fitted on the cheap) will be a good cylinder compression information, so 100 amp hour battery 300 amps cranking. using The pressure pulse transducer first examine the inlet for even pulls of vacuum then the exhaust for equal pushes of pressure and finally the dipstick hole for piston leakage this can all be done non-invasively and about five minutes I personally have not used an in cylinder tester for mechanical engine conditions for two or three years PS You mentioned cylinder leakage on a head gasket failure using the pressure pulse transducer held in the header tank of the cooling system without it even being sealed you will see pressure pulses from escaping gas into the cooling system and just a guess at 33.50ish you talk about the bump could it be as the bid end moved outward the piston speeds up and pressure drops quicker over given time and the burn has finished best regards hope this helps somebody And Matt if want a piezo pulse sensor email me and no i dont sell them so not trying to drum up business
Hey thanks John and good to see you again. Yes I’ve evolved since we last talked hahahaha. In fact I think I may have even exchanged words with you on the validity of compression tests in fact. Thanks for your knowledgeable comments and glad you are back!!
Absolutely excellent video Matt. The extent of your explanations and opinions of why something is happening is second to none that i have seen. Paul and Eric do great, but i believe you have nudged them into second place, lol. Pine Hollow is another channel ive picked up lately. Iven i think his name is.
Thank so much and what an honor to be included in that group. Yes I know Ivan. He actually has a PhD in some engineering field so he also has that “academic” background that makes his videos more educational.
I would like to say that pressure transducer is a VERY POWERFUL tool in diagnosing. BUT, its expensive to buy the scope and keep a dedicated laptop updated and running throughout time. Plus the schooling required to be able to learn readout and how to operate it. My compression tester has sat in a box waiting to be used for a decade now at a cost of $100. With all that said, I think it's time for me to make the investment. 🤣 I do programming with J2534 for Ford/GM. Maybe I will see if I can use the same dedicated laptop with a Pico. I have gotten by 25 years wrenching as a diy without the new technology of an in pressure transducer. Unfortunately, it has cost me a ton of time to not have that technology, but now I have the experience of working with a standard compression tester and its limitations. First, a compression tester will not pick up a partially wiped out lobe or partially compromised valve issue. It will pick up a broken valve spring and that will generally show 0 psi. The engine will also run terribly with 1 completely dead cylinder. It "usually" will pick up a valve sealing issue, in which a leak down test can show air passage to the exhaust, intake or engine. In that trucks case, the loud tick is the very first thing I would hone in on. Verify it's not an exhaust tick and its pretty much off with its head. (head needs to be pulled on those in order to pull the lifter) One variable would be MDS valve sticking causing a miss. BUT, I do not believe a 2005 Ram has MDS.
Hey good to see you back!! Yes as you are very well aware I went through most of the past 8 years without any of this technology however now I work on no less than 4 cars every weekend and sometimes as many as 8. That’s more than I used to do in 2 months. So I need the technology to do the higher throughout now.
compression test is valid, but you can’t expect more than it can deliver. It can detect bad compression rings/ cylinder walls or leaking valves. And it will only detect a major leak due to warp/erosion of the head and gasket. It may not detect slight head gasket leaks or valves that will not open.
Another great video Matt, Thanks for sharing! That's really cool getting to see the power stroke, I've never worked on one of the older Hemi's where you can still have a spark plug in. The newer ones have a COP with 2 boots coming out of it.
Yes that was interesting indeed and the last car I worked with that had two plugs per cylinder was like you said- one coil for both so it too challenging to set up the single spark without risking potential shock to my transducer. This was a great opportunity though!!
in the south its quite common to see people buy shorty wires and instead of going to companion cylinder they just go to the other plug same cylinder. you probably have a broke valve spring or warn camshaft those years didn't give much cam problems it was mostly after MDS.
I think that the expansion and heat of combustion gases is prolonging the increased pressure reading of the falling phase of the trace. The composition and temperature of the gases are different between the intake and power stroke for these measurements. During the traditional test where there is no combustion the gas composition does not change and there is no exothermic reaction, so the rising and falling phases are symmetrical and dependent solely on the position of the cylinder. That's my interpretation.
I like to use an old time vacuum meter first. Back when I had a 79 chevy i found the benefit of intake vacuum measurement from a broken intake valve spring...and 3 other RICH cylinders..that were on the same dual plane manifold. This is the 3rd video I saw that implicates the 5.7 Chrysler engine. Based on the other videos you should find a lifter roller bearing that is destroyed. Based on your vacuum reading lumpiness I suspect many other cylinders that are also having problems, and the complete engine has had a steady diet of metal glitter throughout. The cam will be destroyed also. The misfire code itself is the incorrect name for what can happen. There is no misfire in this case, but compared to the other cylinders there is a velocity change, a lack of acceleration on #1,as compared to the others. The crankshaft position sensor picks this up, and sets a misfire code., nothing at all wrong with the spark, but surely a reduction in air while running, if bad enough it might cause a darker plug. Vacuum gages are so easy to use, they should be the #1 tool to qualify the valvetrain. Great video, my friend has this exact problem with his Ram !
Awesome find. I wish I had a pico with their transducer. I have the snap on edge with my home made transducer. It works ok but the image quality of the pico is insane. Hope my health starts to improve and I can finally start making more money. I enjoy the channel and scannerdanner is a amazing guy. I had a chance to talk to talk with him😊
Nice diagnosis Matt! Can't beat what a pressure transducer & intake pulse sensor can do for you. Can a person without a scope & transducer use a compression test, leakdown test & your ear to fix this...absolutely but in our profession it's all about quick diagnosis & using the scope to prevent disassembly on an engine that needs to be rebuilt or replaced to save the customer $$.
But I’m thinking - the compression test didn’t show it. And also how would a leakdown test possible show it- the valves are closed during compression!!
@SchrodingersBox Yes I agree with you it would pass & they could eliminate that but then the senses come in. Listening to it ticking noise is just another clue valvetrain related lifter collapsed, rocker/cam follower, pushrod bent or cam lobe. For those w/o transducers, the ability to do a relative compression test, vacuum test & leakdown test will at least give them some insight & process of elimination & rely on their senses. I agree with you. I rely on every advantage I get from diagnosing equipment
Wow, you're in Denver, that makes me feel giddy knowing I will possibly bump into you That's crazy I recently subscribed to quantum mechanics and absorbing all the information I can, I am not fond of people that want to throw parts at their car, its wasted time and money so I am learning to help my family when they need it
Its a 2005. 2009+ HEMI are the ones that eat camshafts. Not to say it cant, but it is not common on the 2008 and down. I saw it 1 time on a police car that had 20k hours. Cam lobe was wiped on 1 cylinder (2006 engine). The 2008 and down Hemi drops valve seats, and they bounce around in the cylinder destroying the piston and sending garbage via the intake to other cylinders. After watching the complete video, yeah 😆. Something is up with the lifter or cam. Off with its head.
At 34:50 .. Where the power stroke looks strangely different. I think you're just seeing the fire burning and the expansion of gases happening all the way until the exhaust valve opens... That hump on the down stroke of the power stroke almost looks like that's when you're actually getting ignition? Maybe it's a strategy during idle that the ignition timing is severely retard3d?? Because the compression stroke to the peak-- and then even coming back down a bit: all seem the same as a normal test on a dead cylinder (not running)... and then that HUMP is where you're getting a very late ignition.. Or it's getting a normal ignition at or before the peak and that fire burns intensely for the first 1/4 of the way down and that HUMP you see is actually when the burn is finished-- but the expansion still carries on a little more due to the heat, even though the piston is going down. I'm not certain about this though.. It would be cool to see someone who really knows. :) .... All the compression analysis talks/ videos I've seen have always been on a dead cylinder and not on a running cylinder. interesting stuff as always
I found your videos around in cylinder analysis to be a very good intro to the topic. I found another great resource I think others might find particularly useful as well called Pressure Waveform Acquisition and Analysis from the Inside Out by Brandon Steckler. I personally thought the book was well written and worth the money. I’m curious if you yourself have read this book Matt? If not check it out. Also I found his use of piston overlays in the book to fill in the gap on something like what you saw in the intake waveform that might not be so obvious to others. Had you pulled an overlay up with a secondary ignition waveform as a sync I think it could have driven the point home. Let me know if you’re interested in a free overlay program I wrote.
I would love to check out the program!! My email is schrodingers_box@yahoo.com Yes in retrospect I really should have added an ignition synch to the waveform!!
@@werner.x yes it can be done without the program you just need to do some math yourself. I prefer the program and that’s why I wrote it. The main reason is I want to spend all of my cognitive load on the vehicle and not the firing order of the engine and which stroke is which. It gets super confusing fast on a 6 or 8 cylinder engine
Almost forgot some of them have valve seat problems the seats get loose and fall out but sometimes just move down in the cylinder which causes tap because valve closes but is held down some in head thus valve tap it will eventually brake and fall out into pieces
I had a misfire in my 2000 Impala cylinder1 .Injectors good,coils good ,ignition module good,wires good ,compression good.Ran some Sea Foam through it and ran the crap out of it on the highway and misfire GONE .Had another vehicle 2012 Sonic 1.4 misfire it ended up being a broken valve lifter
Why does the good cylinder have lower compression compared to the bad cylinder? The intake valve opens later on the good cylinder. As the piston begins to come up on compression stroke, it actually pushes some of its charge back into the intake manifold, until the intake valve closes. This is why your compression chart has a vacuum pocket at the end of the expansion stroke - there was a loss of cylinder charge (by factory camshaft design.) The bad cylinder closes its intake valve early, and maintains the charge it had during the entire compression stroke, yielding a higher compression. This camshaft design (I believe) gives better high rpm breathing ability. Also, for the running compression with an actual power stroke -- how cool is this engine to afford this kind of testing! It would've been awesome to see an ignition waveform as a secondary channel to the in cylinder pressure. That may have explained the pressure slope changes. Certainly would be interesting to see what the ignition was doing as the slope changed.
Good thought but there is one problem. On a good cylinder the valve opens EARLIER because it doesn’t have to wait to take up the slack on the rocker arm.
Yes but how do you get to the leakdown test when the compression test is negative?? Also where would the leakdown be on this engine? Both valves close.
You rotate the crank(as a former race mechanic, we used a degree wheel) and watch how fast and at what degree "leaking" would occur, and then see if that matches the profile of your cam@@SchrodingersBox
Matt, long time old school mechanic, and I love your channel. I first worked on cars the same year that PCVs became mandatory... :D What is the scanner set-up that you're using? I'm genuinely jealous. Link to a youtube on it would be great!!!
The power stroke seams longer because the combustion gases are expanding keeping cylinder pressure high longer instead of pressure dropping with piston going to bottom dead center. I think the hump is where the combustion completed. But I can see how a complete engine replacement is cost effective. It needed a lifter or camshaft and that is easier to do.
Wait/ so if there is MORE pressure as the combustion expands then how can it move slower if there is more pressure? It would slower with less pressure.
@@SchrodingersBox it's not moving slower. it's actually faster, if it refers to the piston. The graph is showing the rate of decay of pressure,it is not representing the piston speed. In expansion stroke the rate of decay is proportional to the movement of the piston, that gives us the symmetrical graph we all know. But with power stroke, fuel get burnt. With that heat PV=nRT; more heat means more pressure. That additional pressure keeps the cylinder pressure up in spite of piston moving down, so the pressure decay is slower not the piston
The hiccup on the power stroke wave form at 34:04 may be related to what you mentioned earlier. The crank is attached to other running cylinders that may be "slowing the roll" of cylinder #3 on the power stroke.
@@SchrodingersBox I am a beginner. My guess is that this engine is an eight cylinder and two cylinders are on the same power stroke at the same time. The #3 cylinder probably has more compression than its partner cylinder on the same stroke - which is slowing slightly the power stroke push of the #3 cylinder. Probably why it is recommended to keep cylinder compressions within plus or minus 15 percent of each other.
I dont “know” why the compressions higher in the cylinder with the valve issue but its likely due to carbon build up in that cylinder combined with a quarter million miles of uneven engine wear and not at all related to the mechanical problem. Semi-Unrelated, the last hemi I put a cam shaft in I found half of the lifter roller in the oil pan
Nice 👍🏼 ! Absolutely helpful ! Thanks for shedding light on this . What are you going to be teaching on next ? (I’m just wondering out loud / thirsty for more ) . 👊🏼 Looking forward to it !! 😃 I hope you have a fantastic day !!
@@SchrodingersBox Demonstrating the limitations / inconclusive nature of the relative compression test made me wonder about alternative tests such as in cylinder compression gauge test (at idle , 2500 rpm , and snap throttle) , pinpoint leak down test and vacuum gauge test (at idle , 2500 rpm and snap throttle) , and lastly ; ignition waveform analysis … My specific interest is wether or not these three tests would have outperformed the relative compression test in this particular case ?
How is it that the psi in the cylinder when running isn't far higher than when not running? When you disconnected the fuel injector on #1, there was a drop in rpm. This indicates there was some contribution from #1. Excellent excellent video!
It’s because you have very limited intake into the cylinder at idle- the high vacuum in manifold and minimum throttle body opening. During cranking you have open throttle and slower engine speed with no vacuum- more air into cylinder. If you run engine and open throttle then yes- you do get much higher compression. But not at idle.
It's hugely disappointing that the first mechanic didn't even bother (or didn't know how) to test the coil before replacing it, or to simply switch it with a coil from another cylinder and see if the misfire changed cylinders or not. If not, that would've obviated the need for 'new plugs and wires and coil'. Far too many mechanics out there are on the 'earn while you learn' program, and the customers are paying for their ignorance.
Your running intake vacuum waveform shows massive valve lift problems due to the high mileage. Each main peak should have 2 peaks and the peak on the left should be slightly higher the the peak on the right. You can also measure the time between the 2 peaks for cam/valve lift timing. Adding in the CKP will show other timing issues. Cheers.
Your hump on the down stroke of the expansion/power ramp, when is the piston moving the fastest? At the 90* location halfway down the cylinder so there is an increase in speed at that location compared to TDC areas and BDC areas which does not change speed at all during connecting rod rollover. Also DO NOT make scientific deductions without more testing and waveform comparisons, especially with this high mileage and that shitty vacuum waveform all out of adjustment. You are talking about a time issue on the power stroke without using your rulers and relying on your visual fallacies for complete accuracy but I do like your scientific method of getting more members to comment on the YT algorithm, cheers.
this commit is just ingeneral about your channel. Thank you for explaining how the systems on a car works. I have my frist scan tool and a challenging problem that I have a chance to under stand. your video on short term trims and long term trims helped alot. My truck will not enter into the close loop it is staying in open loop. it has code p0171 and p0174 it took me some time to understand why only short term trims where displaying and long term trims were 0. I am going to use the scan tool to look at the car that is working and compare to the broke one. I will be watching more videos on open and close loop and how it changes from one to the other. do you have any videos suggestions that should watch.
If it’s not going into closed loop some things you will want to look at on the scantool are O2 sensor voltages- if your O2 sensors are stuck lean they may not go into closed loop. Also check engine temperature. If coolant temp sensor isn’t showing activity it won’t go into closed loop because of perceived low temperature (not warmed up yet) Also a final thing is maybe you also have misfire codes. If the engine is misfiring then it may go into a special open loop called “open loop 2” which prevents closed loop operation during some engine faults. When you fix the lean issues and any other of these possible issues it should then go into closed loop again.
@@SchrodingersBox Thank you very much! I appreciate and doesn’t surprise me that you are responding to someone who needs help. Idk anyone else who does.
The compression test around the 8 minute mark, the graph was consistent with two high peaks, then two ever so slightly lower peaks. It was repetitive across the graph. I wonder if that was showing anything at all. I'm just part way through the video.
I think you're just falsely calling it a "good" compression test. You admitted yourself that "it's not perfect"... and clearly there were a couple of cylinders that are slightly lower on the RC test. So in the future, I would just take note of those "slightly" off cylinders as a sign that something could still be off a bit.... On this I'm guessing that a lifter roller has collapsed and so there's a lot of slop in the travel (which is likely the noise too)-- and that's why there's that delay in the valve opening during the intake stroke and pulls that vacuum spike (as you said). It could also just be a dead cam lobe. I think the reason it is throwing off the RC test with a false positive is because that large vacuum spike acts as a huge pump and pulls in the air much quicker once the valve does open; so it's basically still getting nearly the full gulp of air-- it's just happening during a shorter duration of the delayed valve being open, but with the inrush being at a much higher speed: due to that extra vacuum spike that causes it to really suck in the air quickly once it does open. I still see an RC test (relative compression) -- as valid, just not definitive. because sometimes it will show you an obvious cylinder being down, so that's still useful... We just can't trust it as a proof that everything is "good". So trust a bad test-- don't fully trust a good test without further testing; (especially if there is a slight discrepancy between cylinders). .. Good stuff. (I'm only 15min in, so maybe you end up saying all this already :)
What you said about the compression test at its faults is 1000% TRUE AND FACTUAL! BUT if I can add a point that I would say it's not completely stupid... If it is about the 6th car you have had like this that is out of how many cars in how many years? There are always exceptions to every rule and we need to know that! When doing a compression test and leak down test it's not really looking for if it passes but rather clear and obvious failures! Yes it passed as the valve was closed like it should have been at that point in the test but anything that had been a failure at that point lands on the issue! Yes just because it passes does not give everything a full pass on saying there can't be a problem there I'm just saying that when doing that test it's more about the failure. Meaning I believe that it's probably best to look at all testing in this field as all testing that passes is not passing! We are looking for failures! We know something is wrong and most times when you get sent something it's because people are running all the tests they can and they pass! So they can't figure it out. But you are able to look at things that pass but there is always something that stands out to you that leads you to a spot or point to come up with a way to isolate what is wrong and then come up with a test to prove that failure. I'm just saying I don't think any test is stupid because there are so many different combinations of things that can be wrong on each individual engine that sometimes to get a clear direction it requires a combination of multiple data points to find that one thing that points to one other Little thing that gives you that I GOT IT MOMENT! and most times it is something that is not a part of the testing but it's ALL RELATED! Clearly you take something away there Will be a problem it's just a matter of to what degree! Great information as always though And you know how I end this as always... DID I WIN THE FREE TRANS AM GIVEAWAY? LMFAO! I ALREADY KNOW IT NO! BUT YOU NEVER KNOW YA KNOW!
I’ve found that the oil filters seem to have been sabotaged. Doesn’t matter what brand they all are impermeable. Now the bypass valve in the filters also seems to have been changed so it will not bypass the filter. Theee poor people take car into shitty mechanic and they get screwed and then the new engine gets screwed and they can’t figure it out because the scan tool doesn’t have that option. Have you ran into this problem?
I don’t follow- so you are saying if it’s a dodge and you hear a tick in the engine the engine is toast and that’s it. It can’t be an exhaust gasket leak. A pulley for belt or the timing chain? Low fuel pressure, external spark grounding, or anything else. Nope- tick means toast. Yeah that’s not how I do things for sure.
Ok 45 year master tech- so you use the compression gauge and compression is totally normal. That’s what you would have found, master tech. You do know that right? So now you did your compression test- charge an hour labor for that and have absolutely nothing to show for it. Now what do you do Master Tech?
When you had the incylinder pressure transducer in the bad cylinder i wish you would have snapped the throttle to catch a full spectrum on wave forms for the bad cylinder. Cranking, running and snap throttle at idle
Yeah what David said- once I determined a severe mechanical issue, I didn’t want to risk having a catastrophic failure at my hands doing a WOT. Otherwise I definitely would have done it and we would have seen almost no compression on #1.
No worries. A lot going on in this one and it’s kind of heavy on the math. I think I mentioned it near the end of the video but yeah- the last thing you want is the engine to catastrophically fail in your care so if I suspect any kind of major mechanical issue- and this engine was proven to have one- I never do anything that stressed the engine out so I don’t end up with an uncomfortable conversation on why the customer drove the car to me just fine but now it’s leaving my garage on a wrecker lol.
Since the engine has 2 spark plugs per cylinder, don't you think a power stroke occurred in cylinder #3.. Is not that the reason why the expansion stroke didn't go lower where the vacuum line supposed to be???..
Yes agreed and I expect as much however what I am really confused on is why the compression and power stroke aren’t symmetrical in time. The power stroke shows a much longer time curve compared to compression. On an expansion stroke the time difference is zero. Why isn’t that so on power stroke?
Hey Matt, have you done any videos on confirming a valve stem seal leak? I've seen the typical responses of if blue smoke appears on startup or coming off load but really looking for a definitive test and I can't seem to find anything out there. I know you can't accomplish it via leak down or compression testing any ideas would help. Thanks
Intruiging to see in cylinder pressure with combustion! Don't want to be guessing, but since no other comments suggested it (except maybe this is what ablackformula was refering to)... could the higher compression on the bad cylinder be due to the early closing of the intake valve? Was under the impression that high performance engines close intake just slightly after bdc, to take advantage of intake charge momentum, to get just a little more. Do road cars do this? If so, then during cranking with virtually no air velocity, that would lead to lower compression, and incorrect early closing would lead to higher compression. Im likely wrong, but would be interested to know why.
Good thought. As for the combustion on the pressure transducer, in retrospect it’s kind of tainted because of having a bad cylinder on the engine. Really need to repeat it with a good engine.
I am a amateur mechanic 100% this could be a dumb question lol but could it be a rebound from something slapping together caused by the extreme amount of valve lash .. I mean maybe I shouldn’t refer to that as lash lol but a bounce between two Two pieces of a metal slapping together .?
4000 series 4 channel pico is what everyone uses; typically costs fourteen hundred or something around there, I think it's 14bit or higher.. but you can get the new rigoI DHO800 (804 or 814 -- are the 4 channel versions).. for four hundred.. They don't have quite as much deep memory, but it is a 12bit scope where all other bench scopes in the past decade have been 8bit-- unless you're paying four grand or more... I researched scopes for several months.. this is basically your best options. Micsig makes a good tablet scope, but it's only 8bit as well; not worth it IMO
Hi mate. Question. As the intake valve is opening a little late and given their is an overlap, wouldn't the cylinder simply draw from the exhaust side, just enough to make up for the intake valve opening a little late?
Yes it does do that a little but remember the exhaust side has almost no oxygen so you might get compression but you wind get combustion and thus the misfire. You are correct.
remind him not all of the 3rd as they call them hemis interchange he will need one that has aluminum valve covers with wires the newer had i think different reluctor wheel
Were these engines prone to cam lubrication issues from prolonged idling? I have a neighbor that lets his pickup idle every morning for 10 minutes until it warms up. It's not a Dodge Hemi, but it still bothers me. 😁
@@SchrodingersBox I saw it somewhere on the internet and it was a police vehicle with the bad cam lobe. ......they idle the cars a lot. ...at Dunkin Donuts 😁 I don't know if it's certain years or if the problem has been fixed. I think it's fine as long as the car isn't idled for long periods on a regular basis.
Speaking of compression, I just replaced the heads on my 06 Silverado. Long story short I went with back with smaller combustion chambers that raised my compression ratio from 9.9:1 to 10.5:1. Factory octane rating calls for 87 octane will I need to now run a higher octane to avoid detonation? Thanks
I just finished installing rebuild head on my 2004 volvo xc90 2.9l T6 , in the first start the car had misfire on 3-4-5 , this engine is from the passenger side is 1-2-3-4-5-6 , I deleted the codes and started again I had same codes misfire on 3-4-5 , I decided to do compression test and it's crazy it's shows 65 on all of the cylinders. my question is if the computer shows misfire on 3-4-5 then how I had same compression result on all cylinder it's not making sense for me . Because 65 is low right ? Shouldn't have misfire on all the cylinders?
This is almost guaranteed evidence of a timing problem. When you have equal low compression on all cylinders the most likely explanation is a jumped timing belt or change which will change the valve openings equally for all cylinders.
@SchrodingersBox oh my god I swear I felt I did the timming off becausei could see 1 tooth off on the exchuast side .thanks a lot I will correct it first thing in the morning 😢 I almost had heart attack because of this T6 engine they fitted in awkward configuration.
Matt, great video as always, but the compression test simply isn’t revealing the issue…it is not lying. Big difference. Like any diagnostic test or other data source, you can use it to rule out what the problem isn’t. A good compression test doesn’t mean you don’t have a valve lift issue on the bad cylinder, but the pressure test with the scope doesn’t tell you which cylinder is bad either…you needed evidence provided by the misfire data as well to narrow it down to a specific cylinder (or use the scope with a CPS or similar). That is the nature of diagnostics and the scientific method. IF the cylinder was down on compression, you are done. The scope provides much more insight, but also requires additional interpretation and understanding, and still requires additional discovery as to the cause (excessive rocker clearance, collapsed lifter, bad cam lobe, etc.).
Yes that’s my point. It’s not lying- there is no compression issue under the conditions of the test. It accurately reported this. But it is misleading in that there is a compression issue causing the misfire.
@@SchrodingersBox but, Matt…it is NOT a compression issue. Your own data showed that. It is an air to fuel ratio issue. The low flow of air into that cylinder as a result of the valve improperly opening results in a rich condition on that cylinder, causing the misfire. The other cylinders on the shared bank will be leaned out as a result of this (but likely not enough to misfire, particularly on a V8).. You can confirm this by looking at the fuel trim data.
@@SchrodingersBox the compression test measures static compression, which is fine. Yes, you are correct in that the actual cylinder pressure of the running engine will decrease on the bad cylinder as a result of the low lift and duration on the bad cylinder. But recall that combustion is a chemical reaction; the stoichiometry is now incorrect relative to the base map. Without an oscilloscope and dynamic cylinder pressure measurements, you can determine the issue with this engine using fuel trim data as well using your OBDII scanner. Easy enough to verify. Scientific method.
Sure you can do that!! The thing is you have to remove the cylinder head on this vehicle to access the lifters. So regardless of whether you find the cam is worn or the lifter is dead - either way you would replace both given the labor involved. So once I determine the issue is lifter related - it was game over.
A lot of people don’t know this old timer is due some of the educated new text out there do all you have to do is look at the block see which head sets the furthest that’s your number one
I know this is outside your wheelhouse but figured I'd give it a shot. 1972 f100 with 300 I6 has a random misfire issue. I've done all the usual things but it didn't fix it. Through dumb luck I realized if I jiggle the key and switch it goes away so I replaced the ignition switch but same issue but goes away if I jiggle it. All the wires look fine and tested fine on my dvom. Any suggestions? Points system, by the way.
@@SchrodingersBox I'm thinking it's spark because the misfire goes away if I bypass my ignition switch. I got a brand new switch and it still misfires with this one, so I'm guessing a wire might be broken inside the insulation or something like that. It's gotta be the switch or the switch on power wire correct?
@@SchrodingersBox I've gotten 11.2v switch on and 12.2/12.6 running. I just noticed my alt light is dimly light and the alt warning light goes out when I press accelerator pedal. Also, I just realized one of the wires from ignition switch is hot to the touch after letting it run for a few minutes.
Hahahaha. Yeah it’s totally in my nature. There is ALWAYS a rational explanation for EVERYTHING. we just don’t always know what that explanation is- but there is one and only one method to find out.
No it is based on the starter amperage. The more compression the higher the starter amperage and the graph is showing those amperage peaks for each cylinder.
You could however remember you have a lot of issues with that- first, with this many miles on the car you now have the issue where you have a new head on one bank and a 236K mile head on the other bank which can cause an induction imbalance. You also have the issue that if you look closely (didn’t show in camera) the oil had “glitter” in it, meaning there will be rapid bearing wear.
That’s possible for sure. There was of course a time not long ago that I would have done an autopsy on this when repairing it but I no longer do major engine work anymore due to time constraints. I only do the diagnosis now and then it’s up to customer to decide what to do from there.
Im lazy and didnt watch this video/segment on why compression tests are stupid to you. But im here to add theres such thing as a running compression test... Last video all i saw was static compression tests being done. Running compression tests can show more and are often overlooked.
@@SchrodingersBox Awesome that should be fun. hypothetically speaking, i wonder what would happen to shadetree mechanics who dont believe in diagnostics if the future was fully electric? 😂 Prob could find a sensor or two to replace
You know Matt tells things straight up when he quotes himself being wrong in the past and tells us why. Really an interesting channel not just from the standpoint of auto mechanics but even more so from the application of a scientific process in troubleshooting anything. Now I know why old rams have such little resale value. I don’t know this kind of stuff, I just tune in for interest and to learn. I was going to guess lack of valve overlap (maybe not in those terms) causing the higher compression. I don’t get it: While one cylinder has a power stroke another one has an expansion stroke. How could they have different times?
You don’t know it’s a mechanical problem. An external ignition short makes that sound. A leaking exhaust manifold makes that exact sound. A bad pulley can do it. We are all experts after the fact.
@SchrodingersBox I know tht know & I do too after ur tests with technical equipment..I was referring to the compression test for ur average joe.Tht would of told the same thing ur technical equipment did..Ur good but really really technical...A compression test is not stupid..
Wait- how is a compression test going to show what my scope did? Please explain. We saw that the compression was totally normal. So how would a gauge show anything different?
I WOULD GUESS 90% OF ALL THESE PROBLEMS ARE SPARK OR FUEL ISSUES. WAY TOO MUCH BULL CRAP ON THESE NEWER ENGINES THESE DAYS. TOO MANY STUPID CENSORS AND MODULES TO MESS WITH. WHAT IS MORE STUPID, IS THE FACT THE E P A MANDATES THESE EXTRA PARTS ON CARS AND TRUCKS, THAT COST THEM NOTHING, BUT COST THE CONSUMER THEIR ASS!!!
I’ve found that the oil filters seem to have been sabotaged. Doesn’t matter what brand they all are impermeable. Now the bypass valve in the filters also seems to have been changed so it will not bypass the filter. Theee poor people take car into shitty mechanic and they get screwed and then the new engine gets screwed and they can’t figure it out because the scan tool doesn’t have that option. Have you ran into this problem?
![Hunxho - Ball Forever [Official Video]](http://i.ytimg.com/vi/nki9ZTF9Uls/mqdefault.jpg)
![Misfire Diagnostic Fundamentals [98 Toyota Camry]](/img/1.gif)
I JUST finished fixing the exact same problem on a 5.7 Hemi. The lifter roller bearing had seized up locking up the bearing and then chewing away at the camshaft lobe, only mine was the #5 intake. Everything else identical. I didn't use a pressure tranducer, nor do I even have one so I will let others answer with a confident answer to your questions about the waveform, but judging by watching the rocker movement in your video and what I found on my repair, I believe what you are seeing is due to a change in the dwell timing of the valve opening and closing. The damaged lifter/camshaft lobe causes the valve to open late and close early. This has got to have an effect on the waveform in some manner. Great diagnostic on your part - you got to the problem much sooner than I did!
Best RUclips mechanic by far been watching this channel for years from the fuel trim diagnostics days lol keep up the great work matt
Well thank you!!!! There are better out there but I am going to make the claim for the easiest to understand explanations!!
You're not going to believe this. I just watched "Pressure Waveform Acquisition & Analysis From the Inside Out". 96 minutes will answer pretty every question you ask yourself during this excellent video. I was blown away by the coincidence of seeing your presentation and then stumbling upon this one. I hope you watch it and like it.
Wow great call. I did watch it just now and you are right- it’s an awesome resource for waveform analysis!!! I bought the book!!
MAP cranking WOT is atmospheric,
MAP running at idle is about 1/3 of atmospheric
therefore compression at idle will be about 1/3 of that cranking.
You did footnote this in the video.
Engine rpm will have little effect on compression pressure between 300 cranking and 600 idling.
At 4000 peak torque rpm (where the engine breathes best (best volumetric efficiency) compression will be highest. There is an interaction between valve timing and air pulse flow that causes peak pressure at peak torque rpm.
34:00 It's not that the piston takes longer , it's the pressure is higher during combustion. The pressure left over before the exhaust valve opens is what causes the exhaust sound we love.
Don't try snap throttle with your expensive pressure transducer. Think of the temperature fluctuations it goes through from compression let alone higher combustion temperature/pressure.
It was a good experiment to try once because you could.
The reason you have high compression in cylinder one is that the intake valve is closed properly but it’s not opening properly thus the compression is high because we are measuring the pressure at the compression stroke witch requires both valves closed and the piston at tdc wich fits the requirements for a good compression when you unplugged the harness for the fuel nozzle the engine speed changed which indicate that the cylinder is working but with a little amount of air fuel mixture results in a poor power stroke because of the tiny opening of the intake valve detected by the crank position sensor signals the pcm to show the miss fire code
Please correct me if I am wrong
Thank you Matt for your efforts in teaching us a lot
Looking forward for your next video
Great in depth video as always, very informative and easy to understand. If you look at the data on the compression test, you can see there is an anomaly on one of the cylinders - the test does show pretty much the same amount of compression throughout all the cylinders but on the pressure build up and let off there is something different. It isn't a smoking gun but there is a pattern in there
Ah yes I see it now, good observation. Didn’t think of it at the time as I just about ruled out compression on first glance.
It does demonstrate that a standard gauge would not have detected any compression at all.
@@SchrodingersBox Where did you notice this anomaly? You mean measurements with a current probe. I can't see at what point it is different.
240,000 miles on a 5.7 hemi. My first check would be a lifter camshaft problem. Especially when u hear the mechanical knocking or ticking
I like to have as many diagnostic "windows" open as possible. When one "window" can't verify the exact issue, I try a different window. The thing is, these "windows" are limited in what they will reveal to us. There is no "wrong" window, it's knowing the limitation of what that window can reveal. Great video Mr. Matt!!!!
Hey Paul great to see you. Yep I agree. I also like the idea what when you are on the right track, all the windows line up and support the same conclusion!
@@SchrodingersBox LOL, when they line up!!! How come when mine line up they are always blurry???, lol.
Just to correct you there, Matt - if we've learned anything at all from previous asshat interjections (and we really haven't), it's that the use of a broom handle is far preferable to a screwdriver for listening to an ailing engine. Works every time. 😂
Hahahahahaha I was thinking the same thing Andy lol. That guy who said put the broomstic on the PULLEY!!!!!! Hahahahahaha!!!!
Yep, that's the one! 🤣
Hey, I have used a cut off broom stick handle to smack a Ford AC clutch for diagnostic purposes, and don't try at home, lol.
@@stevestadnik9206you ain’t redneck ‘till you done this
The compression test is where you should start to diagnose most engines. Plus you get a look at the spark plugs at the same time. After that, do a leak down, 2 good important diagnostic tools. You can get a good idea of the mechanic, general mechanical condition of the engine.
Well the thing is you do the compression test on this engine and it shows normal. Even a leakdown test would show normal- the valves close! So now what do you do?
@@SchrodingersBox I’m wondering how you would get a good reading on compression in your cylinder and still be good ? I’m an aviation mechanic and when we see low compression the exhaust valve is almost always the culprit. I’m not saying that it can’t be other thing because it can be multiple things that add up but usually that’s the problem.
Maybe I’m not understanding your statement. Are you asking about what to do if the compression is good and also a leak down test is good also ?
Valve lash ,rings that sort of thing would be next if that’s what your asking.
Sorry I’m not much help . Great Chanel by the way. I always like to check this guy out. Good info.
Thanks for posting.
Mike. ATL.
@@SchrodingersBox Move on and go down the list, at least you know the general mechanical condition is at least fair because you just crossed of a whole bunch possibility's off the list with those 2 tests
The mechanical condition is anything but fair though! It’s catastrophic!!
The intake lift is barely measurable with a duration of less than 1/4 normal plus you can see the rocker arm is so loose the pushrod could be slipped right past it if you wanted to.
Mike the reason the compression still shows good is only because it’s being measured during cranking and at idle. In both cases you have minimal air intake anyway because the throttle is closed and in the case of idle there is also high engine vacuum. So the compression gauge doesn’t see anything different than normal- there is similar induction as usual plus the valves close upon compression stroke. The poor compression is going to only be present under load when the throttle is open and the intake vacuum is gone. The minimal valve lift and duration then becomes a major major issue as the cylinder cannot breathe due to being unable to draw air in.
Very good video you've clearly learned a lot over the last few years one of the reasons you've see compression is you are experiencing atmospheric pressure at 15 PSI ish trying to jump in the cylinder so a little inlet valve open will almost certainly fill the cylinder at cranking also you have valve overlap as you correctly said ,, and you will get some cylinder filling through the exhaust valve
for the people watching this (controversially id go as far as saying in cylinder pressure testing is waste of time) you don't need a thousand dollar pressure transducer you can do all this testing with a piezo pressure pulse sensor around $50 US ( or make you own) I would also say when you're doing your cranking current analysis A general rule of thumb is three times battery amp specification ( not the battery that might have been fitted on the cheap) will be a good cylinder compression information, so 100 amp hour battery 300 amps cranking. using The pressure pulse transducer first examine the inlet for even pulls of vacuum then the exhaust for equal pushes of pressure and finally the dipstick hole for piston leakage this can all be done non-invasively and about five minutes I personally have not used an in cylinder tester for mechanical engine conditions for two or three years
PS
You mentioned cylinder leakage on a head gasket failure using the pressure pulse transducer held in the header tank of the cooling system without it even being sealed you will see pressure pulses from escaping gas into the cooling system
and just a guess at 33.50ish you talk about the bump could it be as the bid end moved outward the piston speeds up and pressure drops quicker over given time and the burn has finished
best regards hope this helps somebody
And Matt if want a piezo pulse sensor email me and no i dont sell them so not trying to drum up business
Hey thanks John and good to see you again. Yes I’ve evolved since we last talked hahahaha. In fact I think I may have even exchanged words with you on the validity of compression tests in fact. Thanks for your knowledgeable comments and glad you are back!!
Absolutely excellent video Matt.
The extent of your explanations and opinions of why something is happening is second to none that i have seen.
Paul and Eric do great, but i believe you have nudged them into second place, lol.
Pine Hollow is another channel ive picked up lately. Iven i think his name is.
Thank so much and what an honor to be included in that group. Yes I know Ivan. He actually has a PhD in some engineering field so he also has that “academic” background that makes his videos more educational.
I would like to say that pressure transducer is a VERY POWERFUL tool in diagnosing. BUT, its expensive to buy the scope and keep a dedicated laptop updated and running throughout time. Plus the schooling required to be able to learn readout and how to operate it. My compression tester has sat in a box waiting to be used for a decade now at a cost of $100. With all that said, I think it's time for me to make the investment. 🤣 I do programming with J2534 for Ford/GM. Maybe I will see if I can use the same dedicated laptop with a Pico.
I have gotten by 25 years wrenching as a diy without the new technology of an in pressure transducer. Unfortunately, it has cost me a ton of time to not have that technology, but now I have the experience of working with a standard compression tester and its limitations. First, a compression tester will not pick up a partially wiped out lobe or partially compromised valve issue. It will pick up a broken valve spring and that will generally show 0 psi. The engine will also run terribly with 1 completely dead cylinder. It "usually" will pick up a valve sealing issue, in which a leak down test can show air passage to the exhaust, intake or engine.
In that trucks case, the loud tick is the very first thing I would hone in on. Verify it's not an exhaust tick and its pretty much off with its head. (head needs to be pulled on those in order to pull the lifter) One variable would be MDS valve sticking causing a miss. BUT, I do not believe a 2005 Ram has MDS.
Hey good to see you back!! Yes as you are very well aware I went through most of the past 8 years without any of this technology however now I work on no less than 4 cars every weekend and sometimes as many as 8. That’s more than I used to do in 2 months. So I need the technology to do the higher throughout now.
compression test is valid, but you can’t expect more than it can deliver. It can detect bad compression rings/ cylinder walls or leaking valves. And it will only detect a major leak due to warp/erosion of the head and gasket. It may not detect slight head gasket leaks or valves that will not open.
Another great video Matt, Thanks for sharing! That's really cool getting to see the power stroke, I've never worked on one of the older Hemi's where you can still have a spark plug in. The newer ones have a COP with 2 boots coming out of it.
Yes that was interesting indeed and the last car I worked with that had two plugs per cylinder was like you said- one coil for both so it too challenging to set up the single spark without risking potential shock to my transducer. This was a great opportunity though!!
in the south its quite common to see people buy shorty wires and instead of going to companion cylinder they just go to the other plug same cylinder. you probably have a broke valve spring or warn camshaft those years didn't give much cam problems it was mostly after MDS.
I think that the expansion and heat of combustion gases is prolonging the increased pressure reading of the falling phase of the trace. The composition and temperature of the gases are different between the intake and power stroke for these measurements. During the traditional test where there is no combustion the gas composition does not change and there is no exothermic reaction, so the rising and falling phases are symmetrical and dependent solely on the position of the cylinder. That's my interpretation.
I like to use an old time vacuum meter first. Back when I had a 79 chevy i found the benefit of intake vacuum measurement from a broken intake valve spring...and 3 other RICH cylinders..that were on the same dual plane manifold. This is the 3rd video I saw that implicates the 5.7 Chrysler engine. Based on the other videos you should find a lifter roller bearing that is destroyed. Based on your vacuum reading lumpiness I suspect many other cylinders that are also having problems, and the complete engine has had a steady diet of metal glitter throughout. The cam will be destroyed also. The misfire code itself is the incorrect name for what can happen. There is no misfire in this case, but compared to the other cylinders there is a velocity change, a lack of acceleration on #1,as compared to the others. The crankshaft position sensor picks this up, and sets a misfire code., nothing at all wrong with the spark, but surely a reduction in air while running, if bad enough it might cause a darker plug. Vacuum gages are so easy to use, they should be the #1 tool to qualify the valvetrain. Great video, my friend has this exact problem with his Ram !
Interesting. I wonder if the glitter could have been found in oil changes if they had been doing them themselves and looking for it.
Awesome find. I wish I had a pico with their transducer. I have the snap on edge with my home made transducer. It works ok but the image quality of the pico is insane. Hope my health starts to improve and I can finally start making more money. I enjoy the channel and scannerdanner is a amazing guy. I had a chance to talk to talk with him😊
Hope your health improves too and how awesome you got to talk with Paul. he really is awesome!
Nice diagnosis Matt! Can't beat what a pressure transducer & intake pulse sensor can do for you. Can a person without a scope & transducer use a compression test, leakdown test & your ear to fix this...absolutely but in our profession it's all about quick diagnosis & using the scope to prevent disassembly on an engine that needs to be rebuilt or replaced to save the customer $$.
But I’m thinking - the compression test didn’t show it. And also how would a leakdown test possible show it- the valves are closed during compression!!
@SchrodingersBox Yes I agree with you it would pass & they could eliminate that but then the senses come in. Listening to it ticking noise is just another clue valvetrain related lifter collapsed, rocker/cam follower, pushrod bent or cam lobe. For those w/o transducers, the ability to do a relative compression test, vacuum test & leakdown test will at least give them some insight & process of elimination & rely on their senses. I agree with you. I rely on every advantage I get from diagnosing equipment
Wow, you're in Denver, that makes me feel giddy knowing I will possibly bump into you
That's crazy
I recently subscribed to quantum mechanics and absorbing all the information I can, I am not fond of people that want to throw parts at their car, its wasted time and money so I am learning to help my family when they need it
Yes I am in Parker, CO. Let me know if you have car issues and maybe we’ll make a video of it!
Those early hemis can have misfires from the camshaft being worn out. it's the got notorious hemi lifter tick which is most likely the camshaft.
Yes not familiar with known issues however the lifters require cylinder head removal so given the labor- yeah, I’d replace camshaft as well.
@@SchrodingersBox those are known to wear out cams and lifters due the cam not getting enough oil so it just eats them up
Its a 2005. 2009+ HEMI are the ones that eat camshafts. Not to say it cant, but it is not common on the 2008 and down. I saw it 1 time on a police car that had 20k hours. Cam lobe was wiped on 1 cylinder (2006 engine).
The 2008 and down Hemi drops valve seats, and they bounce around in the cylinder destroying the piston and sending garbage via the intake to other cylinders.
After watching the complete video, yeah 😆. Something is up with the lifter or cam. Off with its head.
At 34:50 .. Where the power stroke looks strangely different. I think you're just seeing the fire burning and the expansion of gases happening all the way until the exhaust valve opens... That hump on the down stroke of the power stroke almost looks like that's when you're actually getting ignition? Maybe it's a strategy during idle that the ignition timing is severely retard3d?? Because the compression stroke to the peak-- and then even coming back down a bit: all seem the same as a normal test on a dead cylinder (not running)... and then that HUMP is where you're getting a very late ignition..
Or it's getting a normal ignition at or before the peak and that fire burns intensely for the first 1/4 of the way down and that HUMP you see is actually when the burn is finished-- but the expansion still carries on a little more due to the heat, even though the piston is going down. I'm not certain about this though.. It would be cool to see someone who really knows. :) .... All the compression analysis talks/ videos I've seen have always been on a dead cylinder and not on a running cylinder. interesting stuff as always
Ah you might be right about that!! Now in retrospect I wish I put in an ignition timing event.
Absolutely love your vids. My friend counts on
and I count on you. Thank you!!
❤❤❤❤.
.
Thanks!! How kind!!
Hey Matt @schrodingersbox awesome video with the pico transducer very helpful look forward to more like it.
I certainly will!!! The ability to tell in literally 10 minutes what would take a “pro” to do in an hour is hugely powerful!!!
I found your videos around in cylinder analysis to be a very good intro to the topic. I found another great resource I think others might find particularly useful as well called Pressure Waveform Acquisition and Analysis from the Inside Out by Brandon Steckler. I personally thought the book was well written and worth the money.
I’m curious if you yourself have read this book Matt? If not check it out. Also I found his use of piston overlays in the book to fill in the gap on something like what you saw in the intake waveform that might not be so obvious to others. Had you pulled an overlay up with a secondary ignition waveform as a sync I think it could have driven the point home. Let me know if you’re interested in a free overlay program I wrote.
I would love to check out the program!! My email is schrodingers_box@yahoo.com
Yes in retrospect I really should have added an ignition synch to the waveform!!
Could this be done just by adding another scope channel - without some extra software?
@@werner.x yes it can be done without the program you just need to do some math yourself. I prefer the program and that’s why I wrote it. The main reason is I want to spend all of my cognitive load on the vehicle and not the firing order of the engine and which stroke is which. It gets super confusing fast on a 6 or 8 cylinder engine
@@SchrodingersBoxsending you an email now!
Love your videos, but i knew that was a lifter as soon as I seen the 5.7 hemi and heard the tick
Same
I assumed the same.. but I would have still done all the tests to verify it.
@@calholli you don't need to do the tests I'm pretty sure there would a tsb on it
@@DylanL69You ALWAYS need to test. I could have "guessed" what was wrong from experience too...
@@DylanL69 You still have to verify
Almost forgot some of them have valve seat problems the seats get loose and fall out but sometimes just move down in the cylinder which causes tap because valve closes but is held down some in head thus valve tap it will eventually brake and fall out into pieces
I had a misfire in my 2000 Impala cylinder1 .Injectors good,coils good ,ignition module good,wires good ,compression good.Ran some Sea Foam through it and ran the crap out of it on the highway and misfire GONE .Had another vehicle 2012 Sonic 1.4 misfire it ended up being a broken valve lifter
Cylinder 3 waveform also didn't look too good either with leaning towers. You should have done the other bank versus a companion cylinder.
Yeah agreed this wasn’t a good normal control because of the bad cylinder - I need to do this on a good engine.
Why does the good cylinder have lower compression compared to the bad cylinder? The intake valve opens later on the good cylinder. As the piston begins to come up on compression stroke, it actually pushes some of its charge back into the intake manifold, until the intake valve closes. This is why your compression chart has a vacuum pocket at the end of the expansion stroke - there was a loss of cylinder charge (by factory camshaft design.) The bad cylinder closes its intake valve early, and maintains the charge it had during the entire compression stroke, yielding a higher compression. This camshaft design (I believe) gives better high rpm breathing ability.
Also, for the running compression with an actual power stroke -- how cool is this engine to afford this kind of testing! It would've been awesome to see an ignition waveform as a secondary channel to the in cylinder pressure. That may have explained the pressure slope changes. Certainly would be interesting to see what the ignition was doing as the slope changed.
Good thought but there is one problem. On a good cylinder the valve opens EARLIER because it doesn’t have to wait to take up the slack on the rocker arm.
Holy crap we are both in Denver! Nice to know there is another great here!
Hahahahaha am I being compared to you or vice versa though?
@@SchrodingersBox oh no Sir. I am on the Novice side of technician. Learning from experience like yours and some others.
Ohhh hahahaha. There are a lot of people here way better than me, that’s for sure but I appreciate the compliment!!
As rattle-ca-resto stated, a compression test is a START; you then do a leak-down test(get a good stethoscope) to further analyze
Yes but how do you get to the leakdown test when the compression test is negative?? Also where would the leakdown be on this engine? Both valves close.
You rotate the crank(as a former race mechanic, we used a degree wheel) and watch how fast and at what degree "leaking" would occur, and then see if that matches the profile of your cam@@SchrodingersBox
Ah that makes sense. Wow what a lot of work though. I’ll take the scope in 5 minutes.
wish we had these "modern" day tools then, but you work with what you have@@SchrodingersBox
Matt, long time old school mechanic, and I love your channel. I first worked on cars the same year that PCVs became mandatory... :D What is the scanner set-up that you're using? I'm genuinely jealous. Link to a youtube on it would be great!!!
Thanks. I use a number of scan tools but AutoEnginuity is what I used in this video
Wow thank for your incredible analyst
couple years newer they didn't have wires had one coil each cylinder going to both spark plugs
The power stroke seams longer because the combustion gases are expanding keeping cylinder pressure high longer instead of pressure dropping with piston going to bottom dead center. I think the hump is where the combustion completed.
But I can see how a complete engine replacement is cost effective. It needed a lifter or camshaft and that is easier to do.
Wait/ so if there is MORE pressure as the combustion expands then how can it move slower if there is more pressure? It would slower with less pressure.
@@SchrodingersBox it's not moving slower. it's actually faster, if it refers to the piston. The graph is showing the rate of decay of pressure,it is not representing the piston speed. In expansion stroke the rate of decay is proportional to the movement of the piston, that gives us the symmetrical graph we all know. But with power stroke, fuel get burnt. With that heat PV=nRT; more heat means more pressure. That additional pressure keeps the cylinder pressure up in spite of piston moving down, so the pressure decay is slower not the piston
@mkoteb7202 oh wow I like that explanation. Makes sense!!
The hiccup on the power stroke wave form at 34:04 may be related to what you mentioned earlier. The crank is attached to other running cylinders that may be "slowing the roll" of cylinder #3 on the power stroke.
Yes I thought about that after editing. That totally makes sense and I agree. Will need to do this same test of a good engine to confirm!
@@SchrodingersBox I am a beginner. My guess is that this engine is an eight cylinder and two cylinders are on the same power stroke at the same time. The #3 cylinder probably has more compression than its partner cylinder on the same stroke - which is slowing slightly the power stroke push of the #3 cylinder. Probably why it is recommended to keep cylinder compressions within plus or minus 15 percent of each other.
I dont “know” why the compressions higher in the cylinder with the valve issue but its likely due to carbon build up in that cylinder combined with a quarter million miles of uneven engine wear and not at all related to the mechanical problem. Semi-Unrelated, the last hemi I put a cam shaft in I found half of the lifter roller in the oil pan
Nice 👍🏼 !
Absolutely helpful ! Thanks for shedding light on this . What are you going to be teaching on next ? (I’m just wondering out loud / thirsty for more ) . 👊🏼 Looking forward to it !! 😃
I hope you have a fantastic day !!
I’m not sure hahaha- depends on what rolls through the door. Any suggestions what you would like to see?
@@SchrodingersBox
Demonstrating the limitations / inconclusive nature of the relative compression test made me wonder about alternative tests such as in cylinder compression gauge test (at idle , 2500 rpm , and snap throttle) , pinpoint leak down test and vacuum gauge test (at idle , 2500 rpm and snap throttle) , and lastly ; ignition waveform analysis …
My specific interest is wether or not these three tests would have outperformed the relative compression test in this particular case ?
@@SchrodingersBox Hi Matt, I would love to see you do a Key reprogram using your new Topdon. That would be amazingly helpful. Thank you.
How is it that the psi in the cylinder when running isn't far higher than when not running?
When you disconnected the fuel injector on #1, there was a drop in rpm. This indicates there was some contribution from #1.
Excellent excellent video!
It’s because you have very limited intake into the cylinder at idle- the high vacuum in manifold and minimum throttle body opening. During cranking you have open throttle and slower engine speed with no vacuum- more air into cylinder.
If you run engine and open throttle then yes- you do get much higher compression. But not at idle.
Q from a novis? would a leakdown test reveal the problem better then a compression test?
Not on this car it wouldn’t- you would no leakdown at all because the valves still close on compression stroke, making this even more misleading!!
It's hugely disappointing that the first mechanic didn't even bother (or didn't know how) to test the coil before replacing it, or to simply switch it with a coil from another cylinder and see if the misfire changed cylinders or not. If not, that would've obviated the need for 'new plugs and wires and coil'. Far too many mechanics out there are on the 'earn while you learn' program, and the customers are paying for their ignorance.
Your running intake vacuum waveform shows massive valve lift problems due to the high mileage. Each main peak should have 2 peaks and the peak on the left should be slightly higher the the peak on the right. You can also measure the time between the 2 peaks for cam/valve lift timing. Adding in the CKP will show other timing issues. Cheers.
Your hump on the down stroke of the expansion/power ramp, when is the piston moving the fastest? At the 90* location halfway down the cylinder so there is an increase in speed at that location compared to TDC areas and BDC areas which does not change speed at all during connecting rod rollover. Also DO NOT make scientific deductions without more testing and waveform comparisons, especially with this high mileage and that shitty vacuum waveform all out of adjustment. You are talking about a time issue on the power stroke without using your rulers and relying on your visual fallacies for complete accuracy but I do like your scientific method of getting more members to comment on the YT algorithm, cheers.
this commit is just ingeneral about your channel. Thank you for explaining how the systems on a car works. I have my frist scan tool and a challenging problem that I have a chance to under stand. your video on short term trims and long term trims helped alot. My truck will not enter into the close loop it is staying in open loop. it has code p0171 and p0174 it took me some time to understand why only short term trims where displaying and long term trims were 0. I am going to use the scan tool to look at the car that is working and compare to the broke one. I will be watching more videos on open and close loop and how it changes from one to the other. do you have any videos suggestions that should watch.
If it’s not going into closed loop some things you will want to look at on the scantool are O2 sensor voltages- if your O2 sensors are stuck lean they may not go into closed loop. Also check engine temperature. If coolant temp sensor isn’t showing activity it won’t go into closed loop because of perceived low temperature (not warmed up yet)
Also a final thing is maybe you also have misfire codes. If the engine is misfiring then it may go into a special open loop called “open loop 2” which prevents closed loop operation during some engine faults.
When you fix the lean issues and any other of these possible issues it should then go into closed loop again.
@@SchrodingersBox
Thank you very much! I appreciate and doesn’t surprise me that you are responding to someone who needs help. Idk anyone else who does.
The compression test around the 8 minute mark, the graph was consistent with two high peaks, then two ever so slightly lower peaks. It was repetitive across the graph. I wonder if that was showing anything at all.
I'm just part way through the video.
Yeah you almost see variance like that however, especially on an old engine. The compression is within spec…. During cranking.
Had to do a new engine on my 1500 for this exact same thing. Cam and lifter metal all throughout the engine…
I think you're just falsely calling it a "good" compression test. You admitted yourself that "it's not perfect"... and clearly there were a couple of cylinders that are slightly lower on the RC test. So in the future, I would just take note of those "slightly" off cylinders as a sign that something could still be off a bit.... On this I'm guessing that a lifter roller has collapsed and so there's a lot of slop in the travel (which is likely the noise too)-- and that's why there's that delay in the valve opening during the intake stroke and pulls that vacuum spike (as you said). It could also just be a dead cam lobe. I think the reason it is throwing off the RC test with a false positive is because that large vacuum spike acts as a huge pump and pulls in the air much quicker once the valve does open; so it's basically still getting nearly the full gulp of air-- it's just happening during a shorter duration of the delayed valve being open, but with the inrush being at a much higher speed: due to that extra vacuum spike that causes it to really suck in the air quickly once it does open.
I still see an RC test (relative compression) -- as valid, just not definitive. because sometimes it will show you an obvious cylinder being down, so that's still useful... We just can't trust it as a proof that everything is "good". So trust a bad test-- don't fully trust a good test without further testing; (especially if there is a slight discrepancy between cylinders). .. Good stuff. (I'm only 15min in, so maybe you end up saying all this already :)
What you said about the compression test at its faults is 1000% TRUE AND FACTUAL!
BUT if I can add a point that I would say it's not completely stupid...
If it is about the 6th car you have had like this that is out of how many cars in how many years?
There are always exceptions to every rule and we need to know that!
When doing a compression test and leak down test it's not really looking for if it passes but rather clear and obvious failures!
Yes it passed as the valve was closed like it should have been at that point in the test but anything that had been a failure at that point lands on the issue!
Yes just because it passes does not give everything a full pass on saying there can't be a problem there I'm just saying that when doing that test it's more about the failure.
Meaning I believe that it's probably best to look at all testing in this field as all testing that passes is not passing!
We are looking for failures! We know something is wrong and most times when you get sent something it's because people are running all the tests they can and they pass!
So they can't figure it out.
But you are able to look at things that pass but there is always something that stands out to you that leads you to a spot or point to come up with a way to isolate what is wrong and then come up with a test to prove that failure.
I'm just saying I don't think any test is stupid because there are so many different combinations of things that can be wrong on each individual engine that sometimes to get a clear direction it requires a combination of multiple data points to find that one thing that points to one other Little thing that gives you that
I GOT IT MOMENT!
and most times it is something that is not a part of the testing but it's ALL RELATED! Clearly you take something away there Will be a problem it's just a matter of to what degree!
Great information as always though
And you know how I end this as always...
DID I WIN THE FREE TRANS AM GIVEAWAY?
LMFAO!
I ALREADY KNOW IT NO! BUT YOU NEVER KNOW YA KNOW!
I’ve found that the oil filters seem to have been sabotaged. Doesn’t matter what brand they all are impermeable. Now the bypass valve in the filters also seems to have been changed so it will not bypass the filter. Theee poor people take car into shitty mechanic and they get screwed and then the new engine gets screwed and they can’t figure it out because the scan tool doesn’t have that option. Have you ran into this problem?
Really all that when the tick tells you it's the DOD lifter. 10 second diagnosis done
I don’t follow- so you are saying if it’s a dodge and you hear a tick in the engine the engine is toast and that’s it. It can’t be an exhaust gasket leak. A pulley for belt or the timing chain? Low fuel pressure, external spark grounding, or anything else. Nope- tick means toast.
Yeah that’s not how I do things for sure.
Not to be mean, but the valve train noise alone would cause me to use a good old compression gauge. 45 year ASE master tech.
Ok 45 year master tech- so you use the compression gauge and compression is totally normal. That’s what you would have found, master tech. You do know that right?
So now you did your compression test- charge an hour labor for that and have absolutely nothing to show for it. Now what do you do Master Tech?
When you had the incylinder pressure transducer in the bad cylinder i wish you would have snapped the throttle to catch a full spectrum on wave forms for the bad cylinder. Cranking, running and snap throttle at idle
He stated that , in view of his suspicions of a mechanical issue, he didn't think doing a snap throttle was a good idea.
Yeah what David said- once I determined a severe mechanical issue, I didn’t want to risk having a catastrophic failure at my hands doing a WOT. Otherwise I definitely would have done it and we would have seen almost no compression on #1.
My mistake I must have missed that
No worries. A lot going on in this one and it’s kind of heavy on the math. I think I mentioned it near the end of the video but yeah- the last thing you want is the engine to catastrophically fail in your care so if I suspect any kind of major mechanical issue- and this engine was proven to have one- I never do anything that stressed the engine out so I don’t end up with an uncomfortable conversation on why the customer drove the car to me just fine but now it’s leaving my garage on a wrecker lol.
Since the engine has 2 spark plugs per cylinder, don't you think a power stroke occurred in cylinder #3..
Is not that the reason why the expansion stroke didn't go lower where the vacuum line supposed to be???..
Yes agreed and I expect as much however what I am really confused on is why the compression and power stroke aren’t symmetrical in time. The power stroke shows a much longer time curve compared to compression. On an expansion stroke the time difference is zero. Why isn’t that so on power stroke?
sounded like a lag to me along with a dull kachunk. also, the rpm seems high like all have lowish compression
Hey Matt, have you done any videos on confirming a valve stem seal leak? I've seen the typical responses of if blue smoke appears on startup or coming off load but really looking for a definitive test and I can't seem to find anything out there. I know you can't accomplish it via leak down or compression testing any ideas would help. Thanks
I usually diagnose that using fuel trim showing excessive richness at higher rpm’s.
@@SchrodingersBox awesome thanks I'll have to check that out.
Intruiging to see in cylinder pressure with combustion!
Don't want to be guessing, but since no other comments suggested it (except maybe this is what ablackformula was refering to)... could the higher compression on the bad cylinder be due to the early closing of the intake valve? Was under the impression that high performance engines close intake just slightly after bdc, to take advantage of intake charge momentum, to get just a little more. Do road cars do this? If so, then during cranking with virtually no air velocity, that would lead to lower compression, and incorrect early closing would lead to higher compression.
Im likely wrong, but would be interested to know why.
Good thought. As for the combustion on the pressure transducer, in retrospect it’s kind of tainted because of having a bad cylinder on the engine. Really need to repeat it with a good engine.
I am a amateur mechanic 100% this could be a dumb question lol but could it be a rebound from something slapping together caused by the extreme amount of valve lash .. I mean maybe I shouldn’t refer to that as lash lol but a bounce between two Two pieces of a metal slapping together
.?
What is the best scope device you recommend?
Picoscope is hands down the best.
4000 series 4 channel pico is what everyone uses; typically costs fourteen hundred or something around there, I think it's 14bit or higher.. but you can get the new rigoI DHO800 (804 or 814 -- are the 4 channel versions).. for four hundred.. They don't have quite as much deep memory, but it is a 12bit scope where all other bench scopes in the past decade have been 8bit-- unless you're paying four grand or more... I researched scopes for several months.. this is basically your best options. Micsig makes a good tablet scope, but it's only 8bit as well; not worth it IMO
EEVblog did a great video breakdown of the DHO814
Hi mate. Question. As the intake valve is opening a little late and given their is an overlap, wouldn't the cylinder simply draw from the exhaust side, just enough to make up for the intake valve opening a little late?
Yes it does do that a little but remember the exhaust side has almost no oxygen so you might get compression but you wind get combustion and thus the misfire. You are correct.
remind him not all of the 3rd as they call them hemis interchange he will need one that has aluminum valve covers with wires the newer had i think different reluctor wheel
Great advice Howard. I won’t be doing the engine swap (I don’t do those anymore) but I’ll make sure he is aware to inform whoever does it!!
Is the problem cylinder right over the oil filter location?
Were these engines prone to cam lubrication issues from prolonged idling? I have a neighbor that lets his pickup idle every morning for 10 minutes until it warms up. It's not a Dodge Hemi, but it still bothers me. 😁
I was not aware this was a common issue until after the video. Not sure what the cause is that this is so common, but it is indeed very common.
@@SchrodingersBox I saw it somewhere on the internet and it was a police vehicle with the bad cam lobe.
......they idle the cars a lot.
...at Dunkin Donuts 😁
I don't know if it's certain years or if the problem has been fixed. I think it's fine as long as the car isn't idled for long periods on a regular basis.
I don't get it, with that noise I would know it was mechanical and had the valve cover off.
Why wouldn’t you expect an exhaust leak? It sounds exactly like that. So you take the valve cover right off and find nothing…. Now what do you do?
Off topic Matt but out of curiosity what are some of your hobbies outside of auto mechanics. Do you like to ski?
Hahaha I’ve never been skiing and no interest lol. Other hobbies are fishing, camping, and I hate to say but I love video games hahahaha.
@SchrodingersBox haha very cool! Thanks for answering...video games never get old...fly-fishing in Colorado must be really awesome
@@SchrodingersBoxI’d watch your fishing content. Schrödinger’s tackle box.
Hahahahahahahaha. Made me lol on that one!!!!! Would be a great video because You don’t even know what’s in it til you open it hahahaha
Speaking of compression, I just replaced the heads on my 06 Silverado. Long story short I went with back with smaller combustion chambers that raised my compression ratio from 9.9:1 to 10.5:1. Factory octane rating calls for 87 octane will I need to now run a higher octane to avoid detonation? Thanks
Yes at that compression you will need to move up to at least mid level.
@@SchrodingersBox thanks for the input! Many times I ask for advice and receive no response you truly are dedicated to your viewers.
I just finished installing rebuild head on my 2004 volvo xc90 2.9l T6 , in the first start the car had misfire on 3-4-5 , this engine is from the passenger side is 1-2-3-4-5-6 , I deleted the codes and started again I had same codes misfire on 3-4-5 , I decided to do compression test and it's crazy it's shows 65 on all of the cylinders.
my question is if the computer shows misfire on 3-4-5 then how I had same compression result on all cylinder it's not making sense for me . Because 65 is low right ? Shouldn't have misfire on all the cylinders?
This is almost guaranteed evidence of a timing problem. When you have equal low compression on all cylinders the most likely explanation is a jumped timing belt or change which will change the valve openings equally for all cylinders.
@SchrodingersBox oh my god I swear I felt I did the timming off becausei could see 1 tooth off on the exchuast side .thanks a lot I will correct it first thing in the morning 😢 I almost had heart attack because of this T6 engine they fitted in awkward configuration.
Matt, great video as always, but the compression test simply isn’t revealing the issue…it is not lying. Big difference. Like any diagnostic test or other data source, you can use it to rule out what the problem isn’t. A good compression test doesn’t mean you don’t have a valve lift issue on the bad cylinder, but the pressure test with the scope doesn’t tell you which cylinder is bad either…you needed evidence provided by the misfire data as well to narrow it down to a specific cylinder (or use the scope with a CPS or similar). That is the nature of diagnostics and the scientific method. IF the cylinder was down on compression, you are done. The scope provides much more insight, but also requires additional interpretation and understanding, and still requires additional discovery as to the cause (excessive rocker clearance, collapsed lifter, bad cam lobe, etc.).
Yes that’s my point. It’s not lying- there is no compression issue under the conditions of the test. It accurately reported this. But it is misleading in that there is a compression issue causing the misfire.
@@SchrodingersBox but, Matt…it is NOT a compression issue. Your own data showed that. It is an air to fuel ratio issue. The low flow of air into that cylinder as a result of the valve improperly opening results in a rich condition on that cylinder, causing the misfire. The other cylinders on the shared bank will be leaned out as a result of this (but likely not enough to misfire, particularly on a V8).. You can confirm this by looking at the fuel trim data.
The plugs on that cylinder should also be sooty unless recently changed.
@reneneron2971 it is at higher RPMs because of the reduced lift and duration. It’s not a compression issue at idle is all.
@@SchrodingersBox the compression test measures static compression, which is fine. Yes, you are correct in that the actual cylinder pressure of the running engine will decrease on the bad cylinder as a result of the low lift and duration on the bad cylinder. But recall that combustion is a chemical reaction; the stoichiometry is now incorrect relative to the base map. Without an oscilloscope and dynamic cylinder pressure measurements, you can determine the issue with this engine using fuel trim data as well using your OBDII scanner. Easy enough to verify. Scientific method.
Its like if Zack Friedman were a mechanic.
interesting video
Oh hey good to see you back again!!!
Checking camshaft lift with a dial indicator on the valve rocker ?
Sure you can do that!! The thing is you have to remove the cylinder head on this vehicle to access the lifters. So regardless of whether you find the cam is worn or the lifter is dead - either way you would replace both given the labor involved. So once I determine the issue is lifter related - it was game over.
A lot of people don’t know this old timer is due some of the educated new text out there do all you have to do is look at the block see which head sets the furthest that’s your number one
Say what???
I know this is outside your wheelhouse but figured I'd give it a shot. 1972 f100 with 300 I6 has a random misfire issue. I've done all the usual things but it didn't fix it. Through dumb luck I realized if I jiggle the key and switch it goes away so I replaced the ignition switch but same issue but goes away if I jiggle it. All the wires look fine and tested fine on my dvom. Any suggestions? Points system, by the way.
Have you narrowed the issue to fuel, spark, or timing? That’s the first step.
@@SchrodingersBox I'm thinking it's spark because the misfire goes away if I bypass my ignition switch. I got a brand new switch and it still misfires with this one, so I'm guessing a wire might be broken inside the insulation or something like that. It's gotta be the switch or the switch on power wire correct?
What’s the voltage at time of the misfire?
@@SchrodingersBox I've gotten 11.2v switch on and 12.2/12.6 running. I just noticed my alt light is dimly light and the alt warning light goes out when I press accelerator pedal. Also, I just realized one of the wires from ignition switch is hot to the touch after letting it run for a few minutes.
How can you have 12V of ignition signal while running? Where is the voltage drop on the signal?
Hello Sir
What is that scope sampling time you use
generally I use 1/2 second per cylinder.
That would explain the tapping noise
Yes it’s surprising it wasnt a lot louder and more rattly!!!! It almost seems that push rod could just slip right past the rocker!
26:04 you can tell we're listening to a scientist...
Hahahaha. Yeah it’s totally in my nature. There is ALWAYS a rational explanation for EVERYTHING. we just don’t always know what that explanation is- but there is one and only one method to find out.
@@SchrodingersBox there's an even sneakier heuristic - you say 'these data' when a layperson would never treat it as a plural ;)
Ohhhhhhh. Hahahahahahaha!!!!! Ok yeah didn’t even think about that hahahaha!!!!!!
Is the compression graph pattern based on the sound produced?
No it is based on the starter amperage. The more compression the higher the starter amperage and the graph is showing those amperage peaks for each cylinder.
@@SchrodingersBox thanks for clearing the doubt mate👍
@35:26
Until he finds out that the used engine has mechanical issues too....
Cant you just swap a head? Seems like a more cost effective way to me.
You could however remember you have a lot of issues with that- first, with this many miles on the car you now have the issue where you have a new head on one bank and a 236K mile head on the other bank which can cause an induction imbalance. You also have the issue that if you look closely (didn’t show in camera) the oil had “glitter” in it, meaning there will be rapid bearing wear.
@@SchrodingersBox Aha, the sparklies changes things. Was that perhaps the reason the valve lifter seized? I'm curious how that happens.
That’s possible for sure. There was of course a time not long ago that I would have done an autopsy on this when repairing it but I no longer do major engine work anymore due to time constraints. I only do the diagnosis now and then it’s up to customer to decide what to do from there.
How do you check a coil on a 2004 silverado
4…3
Extremely simple. Just check the 12V reference, ground and the input signal from the PCM. Easy as that.
I like this guy😂!
What’s not to love eh?
How to do compr test on diesei engines..no spark plugs.
Never seen a diesel. Aren’t the glow plugs removable like spark plugs though?
What pressure transducer do you use?
I use a picoscope WPS500.
Hi Matt 👋
hey Tilt great to see you!!!! wow haven’t seen you in a long time!!
@@SchrodingersBoxI've been lurking in the shadows.
I'm super inspired to try out this cylinder pressure testing.
Very good mat you ar sore good mate 👍 Billy cars😂😂
Im lazy and didnt watch this video/segment on why compression tests are stupid to you. But im here to add theres such thing as a running compression test... Last video all i saw was static compression tests being done. Running compression tests can show more and are often overlooked.
But how is the running compression test going to get past the peak compression reading being normal?
@@SchrodingersBox you watch the needle the same way as the waveform
Super
would u make a video about electric cars or nah
I am actually just getting into that. I will do some videos on those once I get a bit more experience.
@@SchrodingersBox Awesome that should be fun. hypothetically speaking, i wonder what would happen to shadetree mechanics who dont believe in diagnostics if the future was fully electric? 😂 Prob could find a sensor or two to replace
Cam lobes ?
what data indicated cam lobes are the problem?
You know Matt tells things straight up when he quotes himself being wrong in the past and tells us why.
Really an interesting channel not just from the standpoint of auto mechanics but even more so from the application of a scientific process in troubleshooting anything.
Now I know why old rams have such little resale value.
I don’t know this kind of stuff, I just tune in for interest and to learn. I was going to guess lack of valve overlap (maybe not in those terms) causing the higher compression.
I don’t get it:
While one cylinder has a power stroke another one has an expansion stroke. How could they have different times?
Yeah I have the same question!!!! Never made sense to me how there can be different piston speeds.
Self taught fixing cars or schooling
Self taught. I’m not a mechanic.
👍
Overthinking using your scanner, use your ears first. I could have told you you had a mechanical problem by starting it.
You don’t know it’s a mechanical problem. An external ignition short makes that sound. A leaking exhaust manifold makes that exact sound. A bad pulley can do it.
We are all experts after the fact.
Vacuum gauge
To do what?
You've got to B kidding!
Nope. Very serious. the engine is done for. I confirmed with irrefutable evidence in only 10 minutes that this was a valve lift issue.
@SchrodingersBox I know tht know & I do too after ur tests with technical equipment..I was referring to the compression test for ur average joe.Tht would of told the same thing ur technical equipment did..Ur good but really really technical...A compression test is not stupid..
Wait- how is a compression test going to show what my scope did? Please explain. We saw that the compression was totally normal. So how would a gauge show anything different?
You
I WOULD GUESS 90% OF ALL THESE PROBLEMS
ARE SPARK OR FUEL ISSUES. WAY TOO MUCH
BULL CRAP ON THESE NEWER ENGINES THESE DAYS.
TOO MANY STUPID CENSORS AND MODULES TO MESS WITH. WHAT IS MORE STUPID, IS THE FACT
THE E P A MANDATES THESE EXTRA PARTS ON
CARS AND TRUCKS, THAT COST THEM NOTHING,
BUT COST THE CONSUMER THEIR ASS!!!
Which sensors are stupid?
The ones that don’t work. duh.
check valve in compression tester...it wont leak down only up
I’ve found that the oil filters seem to have been sabotaged. Doesn’t matter what brand they all are impermeable. Now the bypass valve in the filters also seems to have been changed so it will not bypass the filter. Theee poor people take car into shitty mechanic and they get screwed and then the new engine gets screwed and they can’t figure it out because the scan tool doesn’t have that option. Have you ran into this problem?
How to do compr test on diesei engines..no spark plugs.