That is why I like your videos, it's not a 5 min video of "let's go directly to here and fix it". Going in depth on everything like you do is how people learn. If people don't understand how everything works, then they start replacing parts without troubleshooting first. There are plenty of videos that say "how to replace a camshaft sensor" when a sensor fault occurs. But what do you do when you waste money on a sensor and it still has the problem??? Ignore Mr Rich's nonsense quote!
I agree. Anyone who tries to diagnose problems on cars for very long is going to take "shortcuts" that their experience tells them to. This video is valuable in the fact that it shows how easy it can be to get off track, not to mention the procedures taught. I particularly like the in cylinder pressure transducer/coil ramp pattern. This video proves that Mr. Danner is more concerned with teaching than looking good on youtube.That earns my trust and my respect. As always, great video!
@ncautoman57 The reason you've never seen this happen with compression in the field is because the customer typically tells you that the car only starts and runs with the gas pedal pressed down a little. Even if the customer didn't tell you that, most technicians will press down on the gas pedal a little if the car cranks but does not start. If you do that, then the engine will start right up. As a technician, you will immediately suspect an issue with the idle air control system (especially if the engine stalls when you let off the gas pedal) and you wouldn't even bother with a compression test.
I've ran across similar problems with the GM 3800, but before testing anything I applied the throttle slightly and engine started and ran. Once it started the IAC started working until the next time the engine was shut down. Next time I run across one of these I'll run an engine vacuum and compression test to see if I experience the same thing as you have here. Keep the videos coming, GREAT information!
As long as the key is off, the car will not start. They actually make a nice jumper tool for doing this. It's just a jumper wire with a button in the middle. Connect one end to the b+ and the other to the starter solenoid terminal, and when your ready to crank, hit the button. Good tool when you are working by yourself.
No start problem because of restricted airflow was new to me! I never ran across one like it but I do like it. Great interpretation of the waveform that is 100% based on solid knowledge about engines, Automotive electricity & electronics, and advanced engine performance. I wish I could make it to Rosedale Technical School. Thank you.
I've recorded all of my classes and put them on my website. www.scannerdanner.com It's called ScannerDanner Premium and I offer a 14 day free trial www.scannerdanner.com/join-scannerdanner-premium.html
@SS-U23 Eventually, if you work in the field long enough, you will see a car come in that won't start because rodents built a nest in the air filter housing. Usually, on those, there will be plenty of clues that are visible as soon as you open the hood.
Mr Danner this is great information! I went out on all my families cars and on my scan tool watched the iac v go wide open when I started the cars. I've done compression test on cars with throtte closed and open and I never got a difference in readings. But I can see the risk and error in that testing method now. This information is diag ammo for me at work :) I'm always watching your videos with my pen and paper. Its really helping me develop my skills THANK YOU!
A big thank you for correcting that wave form as it can save a big head ache going down the wrong path. It goes to show that going back to basics has its merits. Another to top video.
The smartboard is cool, but the program you are referring to is the Picoscope. It is a laptop based DSO. The smartboard just allows me to do everything with a touchscreen.
no doubt, this one humbled me too. I never had a difference before either. just chalk it up as another variable when you have low compression across the board
Great find, Paul. That's some interesting information. I noticed in the video how the compression would stop and 60 PSI and the motor evened out across the cylinders during cranking, but couldn't rationalize why. Thanks again for posting some excellent teaching content.
-continued. I removed the throttle body and I did a close inspection there is a little hole by pass was plug not the iac. wow it is little hole almost like needle I installed back and put back egr valve and has 20Hg vacuum running fine with vacuum. I wanted to share this one with you guys because it is firs time I see some thing like this . I WAS FOLLOWING TESTING METHODS ARE DESCRIBED IN YOUR BOOK , VIDEOS LECTURES AND VIDEOS THAT I HAVE WATCHED IN YOU TUBE . THKS YOU ARE GREAT TEACHER.
Thank you. The accumulation of carbon around the throttle plate modifies the venturi equation - it is a restriction to flow - and the dynamics of intake air flow. Also it could cause to not aloud it to complete close, since becoming an unmeasured air passage at idle. Great video, you are a great teacher, thank you for your hard work.
Thank you too! I do my best to show multiple methods of testing, sometimes the DVOM just doesn't cut it. But I will have more scope DVOM comparisons in the future. Stay tuned
I've always wondered why they say to have the throttle wide open when doing a compression test. It wasn't mentioned at the beginning but I assume the throttle butterfly wasn't open during the test, which allowed intake vacuum to be so high. Just because it doesn't matter much in most engines, we can't assume that will be the case in all. Great demo, I'll never forget that point again.
spelunkerd you must watch as many diy videos as I do I see your comments on ALOT of videos lol... at this point in my life it's my only form of entertainment lol
Started watching ur videos since last month, u hav a great knowledge and good into what u do, u r a good teacher n hav a strong feeling that u r a great human being too, we need more people like you. Thanku for the helpful videos..i am trying to get onto ur premium videos but at this starting point of my auto carrier, its little harder paying every month provided i hav alldata suscription too
Thanks so much! Keep watching the free ones and when you are ready, remember that you are paying around 37 cents per day for an education that is not found anywhere else in the world for this price. Hope to hear more from you!
Paul your simply tge best around i have used some of your knowledge a few times on friends cars and their blown away at how i figure it out. Thanks for the vids
This is amazing and will help me out in my diagnostic on my vehicle. I'm having almost the same issue but my '95'civic 1.5L stalls in the morning at red lights/stop signs intermittently/ rough idle to the point where the vehicle stalls. I replaced my IAC valve ~3 months ago, ran fine for a few days after that then back to the idle issue.
WOW. I'm not a mechanic nor do I claim to be, however I am a pretty good shadetree mechanic and can hold my own with troubleshooting - I didn't see this coming whatsoever. I think sometimes I think that ScannerDanner goes the round about way in order to better educate the class, which is great because it's his job, but THIS is a very good example as to why you want to take these types of troubleshooting routes. Fantastic video!
Some systems only use the crank signal for when to fire the coil(s). Some need the cam also. In either case if the timing belt jumped the ignition firing event will not be at peak compression anymore. Sure the valve timing will be off, but TDC compression will not change
There are adaptive IAC position programs. This is why a lot of cars exhibit stalling problems after a simple battery replacement. The fix for this condition is to do an idle relearn (different procedure for every car) or simply clean the throttle body. This will restore "minimum idle speed" (airflow around the closed throttle plate with IAC passage blocked off). It is this carbon in the throttle body, not the IAC or the IAC passage that gives you the most problems.
Paul, I really enjoy your videos. Are you going to upload your waveform as a known good? We in the field could use it. The iATN knowledge base is one of the best resources out there. Keep up the good work.
Great video! It's nice to see the actual scientific reason for these kinds of situations. I'm going to make a guess on the rotary valve being stuck shut from carbon, but a good tech will use the O scope and bi directional control to prove that true which I'm sure your going to show us in part 2. Thanks Paul for donating your time and knowledge for making these valuable videos.
Ok I have a few questions. First, what is the amperage to voltage conversion on the inductive ammeter you are using? Second, you said it went down but then in the voltage numbers you gave you show an increase?
Another awesome video Paul. Like others here I have not seen this in 30 years working on cars. For me your awareness of the transducer pattern and interpreting it was awesome. For the novice it would have been over looked as the pattern looked good. Measurements where key. We probably will never see this in a drive by wire but the older idle controls are still out there. I was wodering though if there was a base idle setting that needed to be corrected as well with the idle solenoid disconnected? Best tech channel on the tube. Thanks Paul
I think the throttle body (minimum idle speed) was also restricted from carbon deposits, so yeah, a perfect storm. This one was truly crazy, I've never seen anything like it. Thanks for the encouragement my friend, I really appreciate it.
Will do my friend. I just wish iATN would allow for the original psdata file as I took the capture at idle and did a WOT snap to redline which shows the cam timing changes. Not that this is critical info. but it may help someone. Look for it, I'll get it up soon and call it known good.
I'm not completely sure I am following you on your question. I think you have my ebook, so check out Section 1 pages 20, 21 and 22. These are case studies showing ignition timing compared to relative compression (not the transducer, but similar test) Pages 21 and 22 had timing issues. In particular page 21 had a jumped timing belt.
I did. There was a MAF and IAT code only. And I believe someone had unplugged the MAF when they were trying to start the car. So false code and no real help in direction there.
iATN (International Automotive Technician Network) there is a free membership and a paid membership which is $45 dollars per quarter. Worth every penny.
I enjoy watching these older videos and then go to the newer ones. I just started my ASE courses and I’m learning about the vacuum testing, wiring, etc and I’m assuming you are a master ASE certified person if not you should be with the wealth of knowledge you have for troubleshooting and not a parts changer.
@@ScannerDanner shoot I’m still learning even though I’ve been doing mechanic work for over 20 years and there’s always something to learn tips and tricks
What would an exhaust restriction look like on the vacuum? Would it be at/near zero all the time? I've got a car with 25# compression equal +/- 1# across the board, it was running, approx 50 mph, stuttered and died. As it was dying, went from approx 10" vac to zero and stayed there (this is a turbocharged vehicle with a high quality vacuum/boost gauge, and I was looking at it when it dropped out) This is a car with 250k on original turbo, cat, shoot pretty much everything is original to the car - but meticulously maintained, and no codes prior to this event. Thought it might have been a computer issue due to excessive oil level in the crankcase (may have been fuel wash, so changed oil and filter, but now doubt that was cause) , and some strange codes in the ECU. Replaced it with a new ECU, no change, and still no compression. Thanks in advance for thoughts/suggestions, been on it for a month every chance I get... and my summer tires aren't getting any wear this year...
Hi. To check cranking vacuum , can I hook in the gauge to pipe which goes to intake from EVAP (purge valve) , which is connected to charcoal canister? Thanks
If your amperage dropped after disconnecting the alternator then yes you have a bad diode that is causing this condition. Just replace the alternator, you may have some luck on a rebuild, but you will have trouble finding parts and some of these diodes can be impossible to change. BTW the maximum parasitic draw should be no more than 50ma on most cars. This would be .05a. You said your meter read .5amps (500ma) with alt. unplugged? This is still too high. Use a different meter to be sure.
amazing and very resourceful video..you make a great instructor. I have a question that board you are using is so advanced how does it know the mathematical differences of two lines? I thought it was just one of those white boards but this thing does everything,
Ok that was very interesting. My Honda civic has a crank no start problem. Everyone said oh it's the timing belt. But first I did all the checks under the dash. no codes but I had the battery out for charging so that is not surprising. I took it apart far enough to do a visual inspection of the timing belt and it looks really good. No looseness and it has no visible wear. Then brought # 1 up to TDC and checked the alignment and it appears to be perfectly in time. But here is the weird thing every time I do a compression test I get basically low compression but the numbers vary wildly from one test to another. Even checking the same cylinder twice back to back the numbers seldom come close from one check to the next. And when I did the first wet test all the numbers dropped! I have never seen that happen on any car. Then a dry test later the same day showed much higher compression than any of the previous tests and all the numbers this time went up to normal or nearly normal range but still varied from 110 all the way up to 220!!! Same number of cranks and same amount or oil in each. I'm starting to think the gauge I borrowed from a friend may be screwy. So going to Autozone to borrow one tomorrow. For info it has spark, injector pulses and fuel pressure. Pretty much has me pulling my hair out. It was running great then instantly stalled on the highway with no strange sounds or warning, just coasted to a stop and has refused to start or even cough since. I've done the compression test with the gas peddle fully depressed but haven't fully inspected the air intake, could it have sucked up something? I have had the air cleaner apart and tried carb cleaner and priming it by soaking the air cleaner with gas, neither test elicited any attempt at starting. But in both cases I put the air cleaner back together before cranking it. It has a long intake pipe so I think a closer look at that unlikely but potential problem is the next order of business.
lstinthwrld1 Yeah I really considered a sheared key as a possibility, but I put #1 on TDC a half dozen times and checked the cam timing and it was perfect every time. That was he only thing I could think of that could explain the radical excursions in compression readings. I still haven't had it worked on but maybe soon.
lstinthwrld1 Naw that's not going to happen, if the crank gear is spun you can get the cam to line up but 1 will not be at TDC on every check. Still, I might go to the trouble of pulling off the lower cover before I just say fuck it and send it to a shop. Oh I don't know if I mentioned it but since I originally posted I have checked it with a professional gauge and still get wildly different readings from one test to the next. I also checked the rockers each time to verify int and exh were closed for compression stroke.
5" at idle is horrible, I think these are known for timing chain issues. Is there any noise in the chain area? Also I think compression on these quad 4 engine were high, I don't remember ever seeing one this high but 200 sounds legit
I'll be doing more of this for sure, but in the mean time look of John Thorton's pressure transducer DVD. It is a little pricey but worth it. It is about 5 hours of training on this type of testing.
Hi Paul Stupid question.In comparing the peak compression with coil primary current for timing belt jump,if the ignition firing is synced to crankshaft position,how do you explain that it will change with cam and crank out of sync while cranking the engine?would it be firing at the same time regardless of cam position?I know the compression would be a lot lower,but why would it fire sooner or later than TDC if it is not synced to cam position?Have you seen a pattern with actual belt Jumped?:)
On a fuel injected car, for the most part, zero. I have read specs of 2-5" during a crank but that was on carb engines with the throttle closed of course. Fuel injection systems have IAC valves that are wide open during a crank so your really not going to build vacuum. Most of the time I have found it to be a useless test. In fact in 20 years of doing this it is the first time it ever helped me:)
I disconnected the alternator, it looks like it went down. First 0.5v then up to 1.3v I can't be sure wether its the cheap cman amp clamp or true voltage. What should I do if it is the alternator? Is your school like the UTI program we have in Cali, or more like the courses offered in the community colleges?
Thanks so much for posting your very informative videos. PLEASE HELP!!! I will start with the question I am hoping you can answer, explain the backstory and end with the same question to keep things organized. I genuinely appreciate any advice and feedback you can offer. Do you think it is possible for a rodent nest (10"x6" mind you!!) to cause no compression in cylinder 5? I have an expensive problem on my hands. I was driving my 2015 Toyota Highlander (102, 000 miles well maintained with proof of service) it started shaking and check engine light, Check all wheel drive and check traction lights came on. Brought it to our local mechanic and they found a rodent nest on the engine (engine bay I believe), upon further inspection they found that cylinder 5 had no compression, but they weren't exactly sure why and suggested we take it to the Toyota dealership for additional diagnostic. They found the same issue (still don't know why, but they don't seem to think it could be rodent related, but again aren't certain what caused the issue). Because there is no other reason given, do you think it is possible that it could be rodent related? It just seems very coincidental, but because I don't know enough about cars it is hard for me to prove although I am trying to dig up what I can and found you :) Toyota and the insurance company didn't see any obvious wire chews so they closed my claim saying it must be "wear and tear" except I have our steady service records and the mileage is less than a standard lease contract- we have a 2010 Rav 4 with 30,000 more miles that is serviced the same and is running great- the mechanics said this is "very rare for a 2015 Toyota" and said I essentially got the short stick and that cars break, and now I was forced to replace the engine as the only solution ($8,200 +450 in diagnostic fees). Toyota was hoping they would find an actual reason (and of course I was hoping it was rodent related as it would be covered by insurance), but they took out the engine and still have no distinct reason for the engine failure/ cylinder misfire, but said maybe it could be debris that made it way into the engine somehow or a mechanical issue (broken arm??). Anyway because that differs from chewed wires, I reopened the claim thinking it could potentially be nest material (there was lots of material) or mouse food "debris"- there just isn't another explanation at this point. My family has been without our vehicle for almost 1 month and it has really made our lives difficult. Anyway, sorry for the long story, but the insurance company is sending out a "engine expert" tomorrow morning to look at the engine and prob try to disprove that it could be rodent related and it feels like it is my last chance to make a connection and prove that it is possible. I found some articles that say maybe an issue or obstruction in the intake?/ debris somehow getting by the air filter and clogging or making its way into the cylinder?/ debris getting sucked into the air filter then the intake (intake runners or intake manifold)?/ Debris getting caught in the valve train preventing the valves from closing causing no compression?/ a block in the throttle plates??/ Issue with the knock sensor injector?? I will ask more questions tomorrow, do you have any advice on how the rodent nest could have caused no compression in cylinder 5? Thank you in advance, Kristin
Yeah that is a weird one for sure, and unless debris was holding a valve open (which you'd see after teardown) there probably isn't going to be any other way to prove rodent damage. What should have been done before teardown was something called a leak-down test. This is when you put the cylinder at TDC compression and then put air in the cylinder to figure out where your compression loss is coming from (valve, rings or cylinder head gasket). Since they sold you an engine, I'm assuming it was a ring issue? Because a valve or head gasket issue wouldn't necessary need an entire engine? But there are many factors that go into that too. It is very possible the rodent had nothing to do with this issue, but they should absolutely be able to tell you WHY it has no compression in that cylinder. You don't need to be an engine repair expert either to make that determination and again, it should have been done BEFORE teardown. Good providence to you.
If you listen real closely - it sounds like the engine starts for a split second, then dies. Especially about the 14:10 mark in this video. That kinda tipped me off to a restriction after your intake vacuum test. Did you notice that at all? Mostly curious.
hi , how are you? you video should be for every kind of people such as beginners, general people & experienced people.from this video i didn't get much. but the video about coil i appreciated that , it was smart. anybody can get from that video according to themselves. anyway thanks..
In this particular case you can trigger the coil by touching the camshafts signal wire with a test light connected on the positive side of the battery right?
Oh ok, I guess I should have removed the intake then as this is necessary to get to the back plugs. Also you missed the point here. You CANNOT always remove a timing cover to inspect marks. I admitted my mistakes in this video (not opening the throttle) but more importantly there were procedures taught here. Some very valuable techniques that are will be extremely useful in other situations.
HI PAUL if i use jumping wire from Battery pos+ to the 12 volt feed to stater it should crank, not start tha engine even with the key off from the Ign in all cars?
Paul, did you check for DTC's first? or did the low compression sound take you off in the wrong direction as you said? Crazy how a faulty IAC would cause low compression values though! Another very helpful video none the less with some nice very nice pico material!
Paul, when you use the pressure transducer to check the the spark is firing at the right time, is that the same as using a relative compression test and checking where the spark is?
Hi Paul How do you use the transducer and set the sweep and voltage scale.I have a MODIS and believe there is pressure transducer available.Could you upload a set up with your VERUS please.Would that pressure wave form be different with throttle open?You opened a new way of diagnosing mechanical issues with voltage and time interpretation.I am gonna look into it.A burnt valve?a worn camshaft?Interesting. Thank you BTW did you pull a couple of plugs for comparison:):) Awesome
Great video and information. Subscribed right out. So I would have to go through all this to understand why I have zero compression on cylinders 1 and 3 then 180 on Cylinders 2 and 4? Car is a 2000 Toyota Tacoma 4.2L that has never been in shop with 209000 miles on it, was parked for 6 years, fuel pump bad, replaced, started right off, drove for about 30 miles with old gas, oil, and low on coolant, hoping to change fluids right after some warm up (,mistake that my "street mechanic" let me do) car started overheating but was brought back home without letting it really overheat or needle stay up, once it shut off ignition it never started again making exact same noise as in this video; same "street mechanic" came and diagnosed with the compression test. told me I have a blown gasket. Broke my coil wires and I fired him (yeah I know, too late then) I do not want to say he is wrong but somehow I feel he is not right about his diagnostic. Some folks have mentioned the crank shaft sensor, other have told me bad head-valves due to old fluid running through system. I got the car on the side of the house ready for a full engine overhaul, any ideas on what should I look before the fun begins?
No compression on 2 cylinders after an overheat? I'd say the headgasket call is correct. To confirm, fill your radiator all the way, pull one spark plug out on a cylinder with no compression and put air in it while you bump the key over. If you see bubbles or water gushing out of the radiator, it's time to pull the head off.
@@ScannerDanner Well yes, will be doing that before starting tearing down but at this point, whatever it is the car wont start so I have been collecting parts for full engine overhaul because if the head is coming out why not do the whole engine, some tree shade mechanics advised to just do the head but car is 22 years old with 209000 miles original parts on it, I think it gave me an awesome service life and deserves a refresher; my 16 year old wants to drive it and would like it to be mechanically ok if that is the case and if not I still enjoy driving it, that is another baby for me!
Great video. Have a question about the IAC. I know that the pcm uses it to control iddle and start up bypass of air to compensate for the closed trottle plate. Now, if that hole is dirty to the point that a ring is formed around the IAC pintle, would this create a problem with the memory recordings for it in the PCM or there is an adaptive program to compensate for it up to a certain point into the PCM strategy ? Sorry, I am a network engineer and I am trying to figure it out the PCM software.
thank you, for the tip of timing chain, but does not seems to be the problem. I suspected of catalytic converted plug I remove the 02 sensor and did compression again with sensor out while checking the vacuum when it started no changes same vacuum same compression ,I though could be sticky open egr valve and I remove the valve no is closed I started the car with it out and runs fine and my vacuum is 20 Hg now. if I plug the intake passage vehicles died.
That is why I like your videos, it's not a 5 min video of "let's go directly to here and fix it". Going in depth on everything like you do is how people learn. If people don't understand how everything works, then they start replacing parts without troubleshooting first. There are plenty of videos that say "how to replace a camshaft sensor" when a sensor fault occurs. But what do you do when you waste money on a sensor and it still has the problem??? Ignore Mr Rich's nonsense quote!
Must say, I took auto shop for two years. Been wrenching for 20 years. Your awsome!
I agree. Anyone who tries to diagnose problems on cars for very long is going to take "shortcuts" that their experience tells them to. This video is valuable in the fact that it shows how easy it can be to get off track, not to mention the procedures taught. I particularly like the in cylinder pressure transducer/coil ramp pattern. This video proves that Mr. Danner is more concerned with teaching than looking good on youtube.That earns my trust and my respect. As always, great video!
In my 35 yrs as a import field tech I have never seen this happen with compression..Interesting video. Thanks for sharing..
@ncautoman57 The reason you've never seen this happen with compression in the field is because the customer typically tells you that the car only starts and runs with the gas pedal pressed down a little. Even if the customer didn't tell you that, most technicians will press down on the gas pedal a little if the car cranks but does not start. If you do that, then the engine will start right up. As a technician, you will immediately suspect an issue with the idle air control system (especially if the engine stalls when you let off the gas pedal) and you wouldn't even bother with a compression test.
I've ran across similar problems with the GM 3800, but before testing anything I applied the throttle slightly and engine started and ran. Once it started the IAC started working until the next time the engine was shut down. Next time I run across one of these I'll run an engine vacuum and compression test to see if I experience the same thing as you have here. Keep the videos coming, GREAT information!
As long as the key is off, the car will not start. They actually make a nice jumper tool for doing this. It's just a jumper wire with a button in the middle. Connect one end to the b+ and the other to the starter solenoid terminal, and when your ready to crank, hit the button. Good tool when you are working by yourself.
No start problem because of restricted airflow was new to me! I never ran across one like it but I do like it. Great interpretation of the waveform that is 100% based on solid knowledge about engines, Automotive electricity & electronics, and advanced engine performance. I wish I could make it to Rosedale Technical School.
Thank you.
I've recorded all of my classes and put them on my website. www.scannerdanner.com
It's called ScannerDanner Premium and I offer a 14 day free trial www.scannerdanner.com/join-scannerdanner-premium.html
@SS-U23 Eventually, if you work in the field long enough, you will see a car come in that won't start because rodents built a nest in the air filter housing. Usually, on those, there will be plenty of clues that are visible as soon as you open the hood.
Mr Danner this is great information! I went out on all my families cars and on my scan tool watched the iac v go wide open when I started the cars. I've done compression test on cars with throtte closed and open and I never got a difference in readings. But I can see the risk and error in that testing method now. This information is diag ammo for me at work :) I'm always watching your videos with my pen and paper. Its really helping me develop my skills THANK YOU!
Smart man.
this is one of the best channels on youtube for technical info. i dunno why you don't have more hits.
A big thank you for correcting that wave form as it can save a big head ache going down the wrong path. It goes to show that going back to basics has its merits. Another to top
video.
The smartboard is cool, but the program you are referring to is the Picoscope. It is a laptop based DSO. The smartboard just allows me to do everything with a touchscreen.
no doubt, this one humbled me too. I never had a difference before either. just chalk it up as another variable when you have low compression across the board
Great find, Paul. That's some interesting information. I noticed in the video how the compression would stop and 60 PSI and the motor evened out across the cylinders during cranking, but couldn't rationalize why. Thanks again for posting some excellent teaching content.
-continued. I removed the throttle body and I did a close inspection there is a little hole by pass was plug not the iac. wow it is little hole almost like needle I installed back and put back egr valve and has 20Hg vacuum running fine with vacuum. I wanted to share this one with you guys because it is firs time I see some thing like this . I WAS FOLLOWING TESTING METHODS ARE DESCRIBED IN YOUR BOOK , VIDEOS LECTURES AND VIDEOS THAT I HAVE WATCHED IN YOU TUBE . THKS YOU ARE GREAT TEACHER.
First think i thought was slipped cam timing Never would have thought suffocation. Brilliant upload, thanks for enlightening me.
Thank you. The accumulation of carbon around the throttle plate modifies the venturi equation - it is a restriction to flow - and the dynamics of intake air flow. Also it could cause to not aloud it to complete close, since becoming an unmeasured air passage at idle. Great video, you are a great teacher, thank you for your hard work.
I was about to take my lexus engine apart and inspecting timing belt, valves, pistons and what not. Now you saved me week of mucking around. Thanks.
Extremely thorough, superb. I wish my college lecturers were as knowledgeable and as enthusiastic as you!
Thank you. I really appreciate this comment
Thank you too! I do my best to show multiple methods of testing, sometimes the DVOM just doesn't cut it. But I will have more scope DVOM comparisons in the future. Stay tuned
That actually makes me feel better, because in the 20 years I've been doing this I've never seen it either. Thanks for the comment!
I've always wondered why they say to have the throttle wide open when doing a compression test. It wasn't mentioned at the beginning but I assume the throttle butterfly wasn't open during the test, which allowed intake vacuum to be so high. Just because it doesn't matter much in most engines, we can't assume that will be the case in all. Great demo, I'll never forget that point again.
spelunkerd you must watch as many diy videos as I do I see your comments on ALOT of videos lol... at this point in my life it's my only form of entertainment lol
Mr Paul you are awesome. I hope I can be as good as you are in the future, I only have 5 years in the field so I wish Ill be like you.
Thanks man. Hopefully there will be more. I've only really had this channel up since late last summer, so less than a year.
Started watching ur videos since last month, u hav a great knowledge and good into what u do, u r a good teacher n hav a strong feeling that u r a great human being too, we need more people like you. Thanku for the helpful videos..i am trying to get onto ur premium videos but at this starting point of my auto carrier, its little harder paying every month provided i hav alldata suscription too
Thanks so much! Keep watching the free ones and when you are ready, remember that you are paying around 37 cents per day for an education that is not found anywhere else in the world for this price.
Hope to hear more from you!
Paul your simply tge best around i have used some of your knowledge a few times on friends cars and their blown away at how i figure it out. Thanks for the vids
This is amazing and will help me out in my diagnostic on my vehicle. I'm having almost the same issue but my '95'civic 1.5L stalls in the morning at red lights/stop signs intermittently/ rough idle to the point where the vehicle stalls. I replaced my IAC valve ~3 months ago, ran fine for a few days after that then back to the idle issue.
My 91 Honda Civic hatchback base 1.5 did the same now it doesn't start
WOW. I'm not a mechanic nor do I claim to be, however I am a pretty good shadetree mechanic and can hold my own with troubleshooting - I didn't see this coming whatsoever.
I think sometimes I think that ScannerDanner goes the round about way in order to better educate the class, which is great because it's his job, but THIS is a very good example as to why you want to take these types of troubleshooting routes. Fantastic video!
Some systems only use the crank signal for when to fire the coil(s). Some need the cam also. In either case if the timing belt jumped the ignition firing event will not be at peak compression anymore. Sure the valve timing will be off, but TDC compression will not change
There are adaptive IAC position programs. This is why a lot of cars exhibit stalling problems after a simple battery replacement. The fix for this condition is to do an idle relearn (different procedure for every car) or simply clean the throttle body. This will restore "minimum idle speed" (airflow around the closed throttle plate with IAC passage blocked off). It is this carbon in the throttle body, not the IAC or the IAC passage that gives you the most problems.
Thank you very much. I really appreciate this comment.
Paul, I really enjoy your videos. Are you going to upload your waveform as a known good? We in the field could use it. The iATN knowledge base is one of the best resources out there. Keep up the good work.
Es impresionante como hace 8 años ya usabas el transductor first look. Yo hace poco que lo conozco y me parece una herramienta muy útil.
Thank you very much! Honestly my round about way on this one was by mistake. I really thought I had a jumped timing belt. Crazy one for sure.
Thank you very much. I was hoping you guys would like this one. Part 2 is pretty cool too. Look for it sometime on Sunday or Monday.
Great video! It's nice to see the actual scientific reason for these kinds of situations. I'm going to make a guess on the rotary valve being stuck shut from carbon, but a good tech will use the O scope and bi directional control to prove that true which I'm sure your going to show us in part 2. Thanks Paul for donating your time and knowledge for making these valuable videos.
Yes! Just to eliminate this variable of a sticking closed IAC valve.
This is definitely a first for a lot of us, I believe this same engine is used on the same year camry.
Ok I have a few questions. First, what is the amperage to voltage conversion on the inductive ammeter you are using? Second, you said it went down but then in the voltage numbers you gave you show an increase?
Another awesome video Paul. Like others here I have not seen this in 30 years working on cars. For me your awareness of the transducer pattern and interpreting it was awesome. For the novice it would have been over looked as the pattern looked good. Measurements where key.
We probably will never see this in a drive by wire but the older idle controls are still out there.
I was wodering though if there was a base idle setting that needed to be corrected as well with the idle solenoid disconnected?
Best tech channel on the tube.
Thanks Paul
I think the throttle body (minimum idle speed) was also restricted from carbon deposits, so yeah, a perfect storm. This one was truly crazy, I've never seen anything like it.
Thanks for the encouragement my friend, I really appreciate it.
1!¡
Will do my friend. I just wish iATN would allow for the original psdata file as I took the capture at idle and did a WOT snap to redline which shows the cam timing changes. Not that this is critical info. but it may help someone. Look for it, I'll get it up soon and call it known good.
good question. clear signal
No worry man, that was my initial call as well. That was certainly a unique situation in several ways.
u r amazing man
i am a mechanical engineer
and i am really get alot of information from ur videos
i canot say something just thank u :)
I'm not completely sure I am following you on your question. I think you have my ebook, so check out Section 1 pages 20, 21 and 22. These are case studies showing ignition timing compared to relative compression (not the transducer, but similar test)
Pages 21 and 22 had timing issues. In particular page 21 had a jumped timing belt.
Well done !! I was looking down the wrong path at first as well. Thanks for the info.
Thank you, me and my co worker learn alot from you . Thank you
I did. There was a MAF and IAT code only. And I believe someone had unplugged the MAF when they were trying to start the car. So false code and no real help in direction there.
love your honesty amigo what a great class THKS
Excellent diagnostic as always ,but what's the normal vacuum should be show in on a normal engine during cranking ? Thanks
Thanks for the reply. Looking forward to more training.
Thank man! And all the way from Peru, that is awesome.
iATN (International Automotive Technician Network) there is a free membership and a paid membership which is $45 dollars per quarter. Worth every penny.
Nope, never even touched the throttle, but in hind sight that would have been key right?
I enjoy watching these older videos and then go to the newer ones. I just started my ASE courses and I’m learning about the vacuum testing, wiring, etc and I’m assuming you are a master ASE certified person if not you should be with the wealth of knowledge you have for troubleshooting and not a parts changer.
Glad you like them!
@@ScannerDanner shoot I’m still learning even though I’ve been doing mechanic work for over 20 years and there’s always something to learn tips and tricks
Fantastic explanation!
What would an exhaust restriction look like on the vacuum? Would it be at/near zero all the time? I've got a car with 25# compression equal +/- 1# across the board, it was running, approx 50 mph, stuttered and died. As it was dying, went from approx 10" vac to zero and stayed there (this is a turbocharged vehicle with a high quality vacuum/boost gauge, and I was looking at it when it dropped out)
This is a car with 250k on original turbo, cat, shoot pretty much everything is original to the car - but meticulously maintained, and no codes prior to this event. Thought it might have been a computer issue due to excessive oil level in the crankcase (may have been fuel wash, so changed oil and filter, but now doubt that was cause) , and some strange codes in the ECU. Replaced it with a new ECU, no change, and still no compression.
Thanks in advance for thoughts/suggestions, been on it for a month every chance I get... and my summer tires aren't getting any wear this year...
Hi. To check cranking vacuum , can I hook in the gauge to pipe which goes to intake from EVAP (purge valve) , which is connected to charcoal canister? Thanks
If your amperage dropped after disconnecting the alternator then yes you have a bad diode that is causing this condition. Just replace the alternator, you may have some luck on a rebuild, but you will have trouble finding parts and some of these diodes can be impossible to change.
BTW the maximum parasitic draw should be no more than 50ma on most cars. This would be .05a. You said your meter read .5amps (500ma) with alt. unplugged? This is still too high. Use a different meter to be sure.
amazing and very resourceful video..you make a great instructor. I have a question that board you are using is so advanced how does it know the mathematical differences of two lines? I thought it was just one of those white boards but this thing does everything,
Good info... definitely a gate way for out of the box thinking.
Ok that was very interesting. My Honda civic has a crank no start problem. Everyone said oh it's the timing belt. But first I did all the checks under the dash. no codes but I had the battery out for charging so that is not surprising. I took it apart far enough to do a visual inspection of the timing belt and it looks really good. No looseness and it has no visible wear. Then brought # 1 up to TDC and checked the alignment and it appears to be perfectly in time. But here is the weird thing every time I do a compression test I get basically low compression but the numbers vary wildly from one test to another. Even checking the same cylinder twice back to back the numbers seldom come close from one check to the next.
And when I did the first wet test all the numbers dropped! I have never seen that happen on any car. Then a dry test later the same day showed much higher compression than any of the previous tests and all the numbers this time went up to normal or nearly normal range but still varied from 110 all the way up to 220!!! Same number of cranks and same amount or oil in each. I'm starting to think the gauge I borrowed from a friend may be screwy. So going to Autozone to borrow one tomorrow. For info it has spark, injector pulses and fuel pressure. Pretty much has me pulling my hair out. It was running great then instantly stalled on the highway with no strange sounds or warning, just coasted to a stop and has refused to start or even cough since.
I've done the compression test with the gas peddle fully depressed but haven't fully inspected the air intake, could it have sucked up something? I have had the air cleaner apart and tried carb cleaner and priming it by soaking the air cleaner with gas, neither test elicited any attempt at starting. But in both cases I put the air cleaner back together before cranking it. It has a long intake pipe so I think a closer look at that unlikely but potential problem is the next order of business.
TruAnRksT make sure all your keyways and roll pins for your timing gears are intact.
lstinthwrld1
Yeah I really considered a sheared key as a possibility, but I put #1 on TDC a half dozen times and checked the cam timing and it was perfect every time. That was he only thing I could think of that could explain the radical excursions in compression readings. I still haven't had it worked on but maybe soon.
TruAnRksT pull the crank gear. the cams will line up on a sheared crank gear pin.
lstinthwrld1
Naw that's not going to happen, if the crank gear is spun you can get the cam to line up but 1 will not be at TDC on every check.
Still, I might go to the trouble of pulling off the lower cover before I just say fuck it and send it to a shop. Oh I don't know if I mentioned it but since I originally posted I have checked it with a professional gauge and still get wildly different readings from one test to the next.
I also checked the rockers each time to verify int and exh were closed for compression stroke.
TruAnRksT nope, cams will line up every time. I have seen it twice at my shop. I do this for a living. good luck though.
Thanks for the comment!
5" at idle is horrible, I think these are known for timing chain issues. Is there any noise in the chain area?
Also I think compression on these quad 4 engine were high, I don't remember ever seeing one this high but 200 sounds legit
I'll be doing more of this for sure, but in the mean time look of John Thorton's pressure transducer DVD. It is a little pricey but worth it. It is about 5 hours of training on this type of testing.
Hi Paul
Stupid question.In comparing the peak compression with coil primary current for timing belt jump,if the ignition firing is synced to crankshaft position,how do you explain that it will change with cam and crank out of sync while cranking the engine?would it be firing at the same time regardless of cam position?I know the compression would be a lot lower,but why would it fire sooner or later than TDC if it is not synced to cam position?Have you seen a pattern with actual belt Jumped?:)
On a fuel injected car, for the most part, zero. I have read specs of 2-5" during a crank but that was on carb engines with the throttle closed of course. Fuel injection systems have IAC valves that are wide open during a crank so your really not going to build vacuum. Most of the time I have found it to be a useless test. In fact in 20 years of doing this it is the first time it ever helped me:)
I disconnected the alternator, it looks like it went down. First 0.5v then up to 1.3v I can't be sure wether its the cheap cman amp clamp or true voltage. What should I do if it is the alternator? Is your school like the UTI program we have in Cali, or more like the courses offered in the community colleges?
Thanks so much for posting your very informative videos. PLEASE HELP!!! I will start with the question I am hoping you can answer, explain the backstory and end with the same question to keep things organized. I genuinely appreciate any advice and feedback you can offer. Do you think it is possible for a rodent nest (10"x6" mind you!!) to cause no compression in cylinder 5? I have an expensive problem on my hands. I was driving my 2015 Toyota Highlander (102, 000 miles well maintained with proof of service) it started shaking and check engine light, Check all wheel drive and check traction lights came on. Brought it to our local mechanic and they found a rodent nest on the engine (engine bay I believe), upon further inspection they found that cylinder 5 had no compression, but they weren't exactly sure why and suggested we take it to the Toyota dealership for additional diagnostic. They found the same issue (still don't know why, but they don't seem to think it could be rodent related, but again aren't certain what caused the issue). Because there is no other reason given, do you think it is possible that it could be rodent related? It just seems very coincidental, but because I don't know enough about cars it is hard for me to prove although I am trying to dig up what I can and found you :) Toyota and the insurance company didn't see any obvious wire chews so they closed my claim saying it must be "wear and tear" except I have our steady service records and the mileage is less than a standard lease contract- we have a 2010 Rav 4 with 30,000 more miles that is serviced the same and is running great- the mechanics said this is "very rare for a 2015 Toyota" and said I essentially got the short stick and that cars break, and now I was forced to replace the engine as the only solution ($8,200 +450 in diagnostic fees). Toyota was hoping they would find an actual reason (and of course I was hoping it was rodent related as it would be covered by insurance), but they took out the engine and still have no distinct reason for the engine failure/ cylinder misfire, but said maybe it could be debris that made it way into the engine somehow or a mechanical issue (broken arm??). Anyway because that differs from chewed wires, I reopened the claim thinking it could potentially be nest material (there was lots of material) or mouse food "debris"- there just isn't another explanation at this point. My family has been without our vehicle for almost 1 month and it has really made our lives difficult. Anyway, sorry for the long story, but the insurance company is sending out a "engine expert" tomorrow morning to look at the engine and prob try to disprove that it could be rodent related and it feels like it is my last chance to make a connection and prove that it is possible. I found some articles that say maybe an issue or obstruction in the intake?/ debris somehow getting by the air filter and clogging or making its way into the cylinder?/ debris getting sucked into the air filter then the intake (intake runners or intake manifold)?/ Debris getting caught in the valve train preventing the valves from closing causing no compression?/ a block in the throttle plates??/ Issue with the knock sensor injector?? I will ask more questions tomorrow, do you have any advice on how the rodent nest could have caused no compression in cylinder 5? Thank you in advance, Kristin
Yeah that is a weird one for sure, and unless debris was holding a valve open (which you'd see after teardown) there probably isn't going to be any other way to prove rodent damage. What should have been done before teardown was something called a leak-down test. This is when you put the cylinder at TDC compression and then put air in the cylinder to figure out where your compression loss is coming from (valve, rings or cylinder head gasket).
Since they sold you an engine, I'm assuming it was a ring issue? Because a valve or head gasket issue wouldn't necessary need an entire engine? But there are many factors that go into that too.
It is very possible the rodent had nothing to do with this issue, but they should absolutely be able to tell you WHY it has no compression in that cylinder. You don't need to be an engine repair expert either to make that determination and again, it should have been done BEFORE teardown. Good providence to you.
They also suggest taking all the plugs out for a compression test.
Yes, just a new technique I learned.
If you listen real closely - it sounds like the engine starts for a split second, then dies. Especially about the 14:10 mark in this video. That kinda tipped me off to a restriction after your intake vacuum test.
Did you notice that at all? Mostly curious.
nice video never seen that on my 23 experience years thanks for the tip
This was my first one too! Crazy that it affected compression the way it did
just an intake vacuum source. any location is fine as long as it is intake vacuum and not ported vacuum
Great video Paul!
I've never seem anything like that either.
hi , how are you? you video should be for every kind of people such as beginners, general people & experienced people.from this video i didn't get much. but the video about coil i appreciated that , it was smart. anybody can get from that video according to themselves. anyway thanks..
In this particular case you can trigger the coil by touching the camshafts signal wire with a test light connected on the positive side of the battery right?
Oh ok, I guess I should have removed the intake then as this is necessary to get to the back plugs. Also you missed the point here. You CANNOT always remove a timing cover to inspect marks. I admitted my mistakes in this video (not opening the throttle) but more importantly there were procedures taught here. Some very valuable techniques that are will be extremely useful in other situations.
HI PAUL if i use jumping wire from Battery pos+ to the 12 volt feed to stater it should crank, not start tha engine even with the key off from the Ign in all cars?
Paul, did you check for DTC's first? or did the low compression sound take you off in the wrong direction as you said? Crazy how a faulty IAC would cause low compression values though! Another very helpful video none the less with some nice very nice pico material!
Sorry to bother you. Love your videos! Did you disable the fuel system or ignition? and how did you do it?
Could it be possible to catch this problem by watching an engine load pid? Like watching 20hg while cranking?
Thanks for all your videos they helping me a lot like the way you teach and think thank you
Thank you
Paul, when you use the pressure transducer to check the the spark is firing at the right time, is that the same as using a relative compression test and checking where the spark is?
Keep learning an keep teaching bud
Hi Paul
How do you use the transducer and set the sweep and voltage scale.I have a MODIS and believe there is pressure transducer available.Could you upload a set up with your VERUS please.Would that pressure wave form be different with throttle open?You opened a new way of diagnosing mechanical issues with voltage and time interpretation.I am gonna look into it.A burnt valve?a worn camshaft?Interesting.
Thank you
BTW did you pull a couple of plugs for comparison:):)
Awesome
man you are good at this
Great video and information. Subscribed right out. So I would have to go through all this to understand why I have zero compression on cylinders 1 and 3 then 180 on Cylinders 2 and 4? Car is a 2000 Toyota Tacoma 4.2L that has never been in shop with 209000 miles on it, was parked for 6 years, fuel pump bad, replaced, started right off, drove for about 30 miles with old gas, oil, and low on coolant, hoping to change fluids right after some warm up (,mistake that my "street mechanic" let me do) car started overheating but was brought back home without letting it really overheat or needle stay up, once it shut off ignition it never started again making exact same noise as in this video; same "street mechanic" came and diagnosed with the compression test. told me I have a blown gasket. Broke my coil wires and I fired him (yeah I know, too late then) I do not want to say he is wrong but somehow I feel he is not right about his diagnostic. Some folks have mentioned the crank shaft sensor, other have told me bad head-valves due to old fluid running through system. I got the car on the side of the house ready for a full engine overhaul, any ideas on what should I look before the fun begins?
No compression on 2 cylinders after an overheat? I'd say the headgasket call is correct. To confirm, fill your radiator all the way, pull one spark plug out on a cylinder with no compression and put air in it while you bump the key over. If you see bubbles or water gushing out of the radiator, it's time to pull the head off.
@@ScannerDanner Well yes, will be doing that before starting tearing down but at this point, whatever it is the car wont start so I have been collecting parts for full engine overhaul because if the head is coming out why not do the whole engine, some tree shade mechanics advised to just do the head but car is 22 years old with 209000 miles original parts on it, I think it gave me an awesome service life and deserves a refresher; my 16 year old wants to drive it and would like it to be mechanically ok if that is the case and if not I still enjoy driving it, that is another baby for me!
it definitely was for me!
Did you watch part II of this?
This is insane! Great video!
Great video. Have a question about the IAC. I know that the pcm uses it to control iddle and start up bypass of air to compensate for the closed trottle plate. Now, if that hole is dirty to the point that a ring is formed around the IAC pintle, would this create a problem with the memory recordings for it in the PCM or there is an adaptive program to compensate for it up to a certain point into the PCM strategy ? Sorry, I am a network engineer and I am trying to figure it out the PCM software.
This is the main reason I keep old school car's and trucks. It's just not worth the money and hassle.
You gotta wait for part two my friend! It is done just have to edit.
thank you!
thank you, for the tip of timing chain, but does not seems to be the problem. I suspected of catalytic converted plug I remove the 02 sensor and did compression again with sensor out while checking the vacuum when it started no changes same vacuum same compression ,I though could be sticky open egr valve and I remove the valve no is closed I started the car with it out and runs fine and my vacuum is 20 Hg now. if I plug the intake passage vehicles died.
lol you'll be fine my friend. 5 years in is when the money starts rolling in.
Fascinating!
Love it. Thank you for sharing!!