Misfire caused by a vacuum leak
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- Опубликовано: 11 май 2012
- Typical to an intake manifold gasket that is leaking, is an engine misfire, especially with the engine cold. In fact many cars will exhibit absolutely no misfires or idle speed roughness with the engine hot. Some may not even have lean condition trouble codes, in particular with speed density engines (no MAF sensor).
Engine Performance Diagnostics chapter 1 pages 9-14
Symptoms
- check engine light (P0300, P0301)
- misfire especially at low RPMs with the engine cold
- customer replaced plugs, wires, ignition coil and fuel injectors in an attempt at fixing this problem
Fix
- replace intake manifold gasket
Tests shown
- how to perform a cylinder drop test (rpm drop test)
- how to test for spark with a test light
- how to use water to locate a vacuum leak
Tools used
- scan tool
- squirt bottle
Playlist
- (Chapter 1) Misfire ID, Compression Tests, Vacuum Leaks, Fuel Trim, Head Gasket, Restricted Exhaust, Low Power, DMM
• (Chapter 1) Misfire ID...
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• P0506 IAC System RPM b...
- Causes of lean condition trouble codes P0171, P0174 - GM 5 3L
• Causes of lean conditi...
For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available at www.scannerdanner.com as an eBook or paper book.
Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium www.scannerdanner.com/join-sc... There is a 14 day free trial.
On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!
Disclaimer:
Due to factors beyond the control of ScannerDanner LLC, it cannot guarantee against unauthorized modifications of this information, or improper use of this information. ScannerDanner LLC assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. ScannerDanner LLC recommends safe practices when working with power tools, automotive lifts, lifting tools, jack stands, electrical equipment, blunt instruments, chemicals, lubricants, or any other tools or equipment seen or implied in this video. Due to factors beyond the control of ScannerDanner LLC, no information contained in this video shall create any express or implied warranty or guarantee of any particular result. Any injury, damage or loss that may result from improper use of these tools, equipment, or the information contained in this video is the sole responsibility of the user and not ScannerDanner LLC. 
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I really want to say thank You, I have been looking for this vacuum leak for a really long time. Changed my throttle body, injectors,spark plugs,coils, upper intake gasket,and a few other things. Really wanted to find it myself and not deal with a shop, and watched many many vids and thought to myself, I guess it’s compression BUT when I saw your video, I immediately did what you said and it was my lower intake gasket and changed it .It is running so smooth and I felt a relief come over me. Thank GOD for you!!!!!!!!!!!
Bravo Homeboy...you think in the way i think too👍
I feel you on that one, I literally did everything you did. I found an OBD2 reader that does live data. My Short Term trim was eratic and way too high which while idling which means a vacuum leak somewhere. I hope I can find my issue. Videos like this really help the DIYers out here.
I know man, for sure I miss our "daily bread" in the morning. Still haven't found someone as dedicated to share in the word with me. God Bless, talk soon
I knew I liked your videos for a reason! Ain't God great!!! Lol take care bro!
Unfortunately for the car owner this is true. There simply is not enough good technicians in my field and WAY to many parts changers.
Thanks for the great info! This is exactly an issue I have been having. DTCs occasionally tripped due to cylinder 1 misfires on 98 Saturn SL1. I wish I would have watched your video prior to buying new plugs, wires, coil, and injector over the course of a year. I also checked the compression just before buying the injector and it was fine. After the injector didn't fix it I opened my ears to hear a hiss. I then found an intake leak right by cylinder 1 using carb cleaner. It looks like water would be a safer way to go, that's what I will use next time. I am going to consider your purchasing your book. Well done.
Scanner danner, you're a professional. I learned a lot from you. Keep up the up the good work. BRAVO ZULU.
In 35yrs as a tech I have never used water to find an intake leak..I have used oil,brake cleaner, carb cleaner smoke test etc..I can see water is a safer viable option..Thanks for sharing,
Best car troubleshooting video for any car or problem that I've ever seen. Thanks. You saved me lots of money with my Neon.
Good Video,
Found you through Eric The Car Guy. Happy i did, good info and easy to understand. Thank you for posting
Thanks for taking the time to make this video... very good technicians are hard to find & your vid helps me get started on pinpointing the similar problem for my 2002 nissan quest
Danner was my instructor.
Hell of a guy, passionate smart and great to learn from. I'm no longer in the field and still watch his videos. Keeps me interested in diagnostics and sharp on what he taught me. Tell me my man don't look JUST like Karl Hagelin
Thanks Needs!
I really love the content man I've been binge watching you since I found your channel it's really refreshing to see somebody truly confirm a problem and not just replace on a hunch you've taught me a lot of things. I was also very pleased to find out you were a man of God. God bless I wish you and your family the best.
Thank you and nice to meet you my brother 😊
Appreciate you bro, this may be my issue on my 03 forester. Grateful for your input time in this video.
this is a great video, very helpful for us non mechanics. I've got a 99 civic with a miss fire under load and this may or may not help me but it is nice to have another diagnostic tool to track down the problem. thank you I'll be subscribing to you channel for more information. keep doing what you're doing.
Under load misfire will not be from a vacuum leak. For additional help....
It is becoming more and more difficult to answer questions here. I have 80,000 people asking me for help now. So I have created a forum to help you guys better. It is free to join and we can exchange pictures, wiring diagrams and waveforms if needed to help guide you through the process of troubleshooting your vehicle. Thank you so much! Hope to see you there.
Paul Danner (ScannerDanner)
www.scannerdanner.com/forum/post-your-repair-questions-here.html
thank you for commenting and your kind words
It is a great "pinpoint" test. Propane will give you an area, but the water shows exactly where.
Thanks for the comment
I still come back and watch your teaching videos because you are so fucking thorough, detailed and fastidious. You ALWAYS prove your theory. Thank you! Truth told though, when I fix things, sometimes I just accept a good result and move on without being certain.
SD we love you bro. You are one of the best technician I ever know
Wish I saw this video before installing new plug, coil plug, maf sensor on my 08 Lexus ls460. I ended up doing a smoke test this morning and found smoke leaking from my intake manifold. Well at least I'll know I have done a somewhat tune up on my car and I guess I'll change all my gasket to be on the safe side. I'm no mechanic but RUclips, Google, and forums help me out a lot
Thank you! That was the plan, I am trying to combine book material with case studies. I think it helps.
Love this videos. Keep up the good work. Looking for more information on intake temperature sensors and the effect they have on fuel delivery
Thank you so much. I've been looking for all of the information in this video on how to troubleshoot this without throwing parts at my truck.
Piece of cake on that engine. Whole different story on my 3.0L V-6. Great video. Thanks.
Nice nice. Lovin' the vids dan,got my mind goin' :) Especially the 30 min one on the crankshaft fluctuation sensor.
i love the smoke. smoke is great for confirming your repair. i hate come backs and charging twice for what could have been spotted on the first visit
I'm so glad I found the channel. Your knowledge is incredible. Thanks for posting these videos!! Keep them coming :)
As others said, I never tried water for leak testing but it looks like a great idea.
I think this would work better than propane.
Gonna try it now on a problem child car that won't idle too well.
Thanks for sharing.
Great video! I always learn something useful with your vids. Keep them coming!
Great video Paul. It's amazing what a simple thing like water can do, oh and a little common sense and knowledge.
We always use gum cutter. Water seems wrong. Love your videos!
Never had an issue with that. I understand your concern though, just be careful if you decide to use a garden hose. No danger with a squirt bottle.
Good shit. Thanks for sharing Paul. I'm following along in your book.
learn something new everyday! thanks, keep the vids coming!
i would have never guessed to check that on my srt. im going to do that test tomorrow and if that's the problem im going to be shocked. I have spent well over 1000$ fixing stuff that could be wrong.
anytime, thank you!
Thank you my friend!
Thanks so much for the video. I have an '03 Dodge Dakota 3.9 ltr with over 300,000 kms on it. Long story short the fuel pump had to be changed. Just after the pump was changed I had a misfire on #5 cylinder code. Have changed out plugs, cap, rotor. Checked operation of injector using a stethoscope...all injectors were humming away. Did a compression test today and have some wonky numbers from that but that's another story. Bottom line will do the water check on the #5 and see what comes of it. Again...thanks for the video. Cheers.
+oldesarge2000 thank you for watching!
+ScannerDanner sometimes in life it's the simple things that work. Changed out the plug wires did a vacuum check.....seemed to hang a second on the bump but looked good otherwise. It had been a while since I had changed the plug wires. Changed them out and all is good. Hanging my head in shame but hey...if it works I'm good with it. But after watching this video I'm now aware of how an intake manifold leak could cause a misfire situation. Learn something new everyday.
I don't remember who showed me that test, but it is a great test. Especially when you don't have a smoke machine. Thanks for the comment
I don't know what to say, but you are the best boss sir👍
Beautiful. Simple and effective.
Helpful. Others suggest spraying brake cleaner at the leak to listen if the engine will run better, due to the extra fuel. I do believe that making the engine run worse would be easier and more conclusive. Thumbs up for sure!
I more like water test it not make fire. But seem like water test only can do at intake manifold gasket test but not other small leak from other rubber hose. But still good way without any harm.
Hey Dan, I gotta tell ya, your the man dude. Awesome videos. I'm guessing your from the burg somewhere. I'm from Steubenville. Keep up the good work and....keep on scanning
haha yep, about 10 miles south of Pittsburgh and my name is Paul Danner but it's okay, I get "Dan" all the time :-) Thanks Sean!
Excellent demonstration, thank you. 🙂
Sweet man, it probably worked like a charm didn't it? It is a great pinpoint test for sure.
Great test, safe and simple.
Very good development of the theme and accurate explanation !!!
Thank you!
Thank You for this upload. This video was awesome. You're a really good teacher.
+Kaktus Jack thanks for watching and I'm glad it helped you
I absolutely agree. I have some educated people, as well as a couple of clown fools that reply to my channel, and don't contribute anything of value at all. You, sir, kick ass.
My Blazer just developed a misfire and sucked the electrode out of at least one spark plug, so, I'm still trying to sort that out!
Thank you I will remember that it will be quite helpful for that vehicle and that engine thank you.
Fantastic !! Well done as usual.
I know, you can hear her in a lot of my videos. Brings back memories, doesn't it bro.
PRODIGY Sir ScannerDanner
From the start to finish loved it tutorial great video amazing footage thank you very much. Take care and have a great day
PRODIGY Sir ScannerDanner
From Nick Ayivor from London England UK 🇬🇧
Again you killed it awesome vid!! Where do you teach?
Great information and examples.
Ty... awesome info... I like the great tip using spray bottle with water... vs flammable liquid sprays.. I've seen so many cars catch on fire with techs using brake clean.... so dangerous..
Thanks Russ!
Question. I have been able to bypass stuff from some of your videos. I recently figured out my rendezvous has what I believe to be the wrong tranny. The one in it has no modulater valve but is looking for one. Also noticed an empty harness which I believe goes to a TCM. It exhibits shift concerns as well as dies usually in right turns and on the throttle. Also struggles uphill. Is there any way of tricking the ecm to think the correct tranny is in the vehicle?
Scanner danner, you're the man. Intake manifold gasket leak will trigger a misfire.
yes it will. Thanks!
not necessarily intake gasket, I had a time when the injector o-ring was torn in half and was missing the other half, was causing misfires like crazy.
Thank you. I teach at Rosedale Technical Institute in Pittsburgh, PA.
as always very good video brother,GOD bless you!
👍 super helpful as always! Thank you!
on a map (speed density ) engine you can have normal trim numbers with a vacuum leak.
thanks for the info good tip quick question you sometimes refer to using propane is that different to butane in anyway is it safer or more flammable etc
Great instruction and video! Thank you!
thank you!
Great video! Thanks
It is helpful for me,I have my idea for DIY about misfire,thanks.
I've also used the techniques you've demoed for finding vacuum leaks, and in addition have a stethoscope I modified with several different interchangeable open end probes; made of various tubing scraps.
It's far from perfect, but allows me to listen closely around most anything I can see, and some I can't. Running along gasket lines, there is no doubt when a leak is found. Some are dramatic.
It's also great for quickly finding dead/shut off injectors, exhaust leaks, and more.
Good work! Keep it up
Great video man. Are these kind of leaks more common in engines that have overheated at some point?
nope, just a bad o-ring type gasket. Thanks!
I think my original comment got erased or something idk,thank u for this video i will DEFINITELY be back on here after trying this.ive got a spray bottle,now i just need a prayer
New coils plugs, injectors,swapped them all around too,and still cylinder 2 missfires code but also p300 which i didn't get before replacing it all.however it runs better after injectors replaced.the2nd cylinder injector had a crack around knozzle so i saw that and got excited like i found it.well it runs better now and the warmer,the smoother and less spudding or jerking..if I'm smooth and easy with the throttle its good and idles great after warm up.this leads me to believe now there is also a vacuum leak somewhere and i will be trying this in the morning.thank you for this video i wish i found you years ago
awesome test.
Scanner Danner is the man !!!!!
thank you but I'm really not :-)
I think you just diagnosed my issue on my 1995 mustang 3.8l it has a lean o2 sensor reading on only one bank, bogs when cold, and has a low idle. I am going to try this soon. Will let you know the outcome. BUT when first driving, it will begin to bog and WITHOUT changing the throttle position (still under load) the car begins to accelerate back up and run normally. All in the course of maybe 2-3 seconds.
It would have, but I didn't check it. I was focusing on showing the water test.
Paul, is propane still used to detect vacuum leaks and is the turning the engine over listening for relative compression as accurate as actually pulling the plugs and using a gauge? I guess it would depend on someone's experience like you vs someone with much less knowledge--
The expansion of the head and intake stopping/lowering the intake leak would be the same as an exhaust manifold leak that goes away when the engine gets hot
good stuff, thank you...
How do you feel about using a can of carb or intake cleaner and spraying around the gasket to listen to idle raising?
Bravo very good ill try this my car msf c1
That is correct and you will get shocked if you don't give it somewhere to go. It will choose you as the path.
I have the same car 97 2.0 liter sohc neon. I get intermittent cylinder 3 misfires when accelerating to highway speeds. I'm thinking I should swap wires and plugs because, the compression tested good plus i've rotated the injector positions and seen no difference. Plus I noticed minor corrosion in the inside of the wire to coil boot. Don't think they've ever been changed Has 160k miles on it. Also have to do a complete set of motor mounts and replace the egr system and tube in the future.
Wow great video. I'm running on a problem as well with an 03 neon myself. Had a p0301 come on it wouldn't act up in cold start though more when it was fully warmed up. Even at idle it wasn't as much as a concern only happened when I would accelerate. The engine would bog down badly loss of power and then the p0171 came on as well. I noticed my fuel trims go way high when I would accelerate my engine and would bog down. But as soon as I came back and to park the idle was normal and the fuel trims came down again. But only starts to rough idle when I have in drive. I'm assuming that the 301 is cylinder one meaning that problem is in that area and the 171 meaning it's a air and fuel mixture that is incorrect. Which leads me to think one or the other. Fuel injector which u had swapped but no light has come one yet. And two the intake manifold on cylinder one and this video is leading me to believe I may have just that. Also I was wondering is the fuel pressure at idle normal for a neon to be 6-9 psi. I know the fuel pressure at max is around 50psi. But I never do see what the pressure is at idle anywhere. And I get that in my scanner. And also this fuel pump is Brand New from AutoZone it's a Delphi fuel pump
I get 301 or 302 codes after it warms up and (usually) when it's full tank of gas I get a 401 egr code. 04 Nissan Frontier 4cyl. Not every drive, sometimes a few days in between. Any ideas before I start a tune up?
I have a story, which is a puzzle for me and probably for many who reads it. I went to Firestone on
Northway Hwy to do alignment and State Inspection. The car is old, and basically it is my toy-car
to practice on auto DIY projects. 2001 Saturn SL2. The car was running maybe not the best, but
normally, my main concern was alignment, bcs I did a lot of suspension work on the front, and my
husband observing how I move parts around came to the conclusion that the car will never run
again. At Firestone they couldn't do alignment, bcs they needed a special tool (for the rear), which
they didn't have and advised me to go to a dealership to do a proper alignment. To my amazement
they said that the current alignment on the car was pretty good, gave me a print, which proved it. I
assume, the alignment was good, bcs I counted turns on outer tie rod very accurately. They said
that the battery didn't pass the test (car was sitting for a long time), but passed the safety standards,
so I need to make 50 mi on it and come back. I went back home, and on the way I noticed that the car
started to shake slightly at one red light. When I came home the engine was shaking like crazy. I
switched it off, took Actron, but before diagnostic decided to start it again and listen once more what
the engine does. The car started vibrating vigorously, the arrow of the rpm jumping from 400 to
1200 and back all the time, then after a loud sound ("bum!") died. There was a small puddle on the
ground from the transmission fluid. Actron gave P0404 code, which is emission code, so I decided to
clean a Throttle Body, what I did, but there were not much changes. Next morning car died again
on idling, when I warmed it up. Now in addition to P0404 it gave a code for the Powertrain Module
(Engine computer). I started the car again and without any waiting in Idle went to the Toyota
dealership, they did some work on alignment, but also didn't have that tool for the rear of the car,
and advised one GM dealer. I suspected bad fuel, so I added like 1/2 tank to make it full, poured
good engine cleaner, car started to run a bit better, but still vibrating at stops (though at 800 rpm
already). No more leak fm transmission. In that condition (car was still vibrating on lights) I went
to Jupiter Chevrolet Dealership, where they did the front alignment perfectly, some rear, but not
toe (again no tool for that job on the rear). When I started to drive I immediately noticed that the
car runs perfectly well, no rattling, vibration, you could sit like hour in Idle, it runs very smoothly
and good. I went back to thank and ask, what it was, what did he do, but the mechanic gone for the
day. So my question for the puzzle is: what can be done to the car that it develops a vibration on
lights, and see how, not immediately after I left the Firestone, but after about 5 miles of driving?
And what the mechanic at Chevrolet Dealership did, that the car runs with no problems now, very
smoothly and quietly. Later he said that nothing was done besides an alignment, and he never
opened a hood. Thank you for the great film.
Great video thanks
Very good video man.
@scannerdanner update: on 2003 sable v6 duratec, i cleaned Maf, upon start up it went closed loop, stft wher still high average 32 on both banks.. after about 30 sec of running it back to missing at idle and open loop.. I do hear some hissing at back of intake to congested to tell tho, so I'm going to try the oL warter in the bottle trick now..
Hey! Scanner! another well done informative work of art!~ after watching your vids, and your answering of all the different car questions you get here! I've come to the conclusion any car can pretty much be repaired if the mechanic working on the vehicle has thorough knowledge of how a car works~ and that a lot of shops including dealers don't have the experinence or the knowlwdge. so they tell you they can't find anything wrong! or a dealer just wants you to buy one of thier new cars!..LOL!
Thought you said it passed the smoke test? Don't worry about the open loop fault, the PCM will do this if it cannot compensate for the condition. Do the water test as you said.
that a nice unique teat ,I'll try to use it in the school
Hi. Muy chevy 3.4 has rough idle. If i close the trotle body with muy has it doesnt stop. If i unplug the booster conection it istabilises. If I try to open the oil cap I cantón do it un les the cae is off. It coul be a vacuuum gasquet probem?
maybe this is what is going on with a Trailblazer we are working on...it keeps says air/fuel metering, and we replaced the o2 sensor, and it didn't change anything
would that leak have shown up on a vacuum tester?
Hi, do you know why I miss the exhaust and the air filter very hard when I go on the LPG and petrol I don't have much? Noting that I changed the spark plugs and plugs, I cleaned the throttle and the idle valve (air flow meter). Thanks!
Po302 on my 2006 Subaru sti with 150,000 miles. Runs fine. Swapped plugs, ignition coil next is injector swap then leakdown test
Might I ask you about your car / situation ? What was the specific problem actually ? And what was the fix ?
Yes it only misfires when it’s cold! Replaced the dang coil pack and fuel injector when all I needed was a gasket
ScannerDanner, notice how those spark plug wires were improperly routed through those spark plug boots. Aw man.. the guy that did the tune up in the past :D And is that a dodge neon? Nevermind. Interesting video again.
My car has a rough start when very cold outside, but runs smooth until the engine gets hot. From that point, hesitation on the gas, erratic idle, no power.
Hey scanner danner i have a 07 avalanche with 5.3 with misfire. I did a dod delete and took afm out of pcm. P0300 comes up frequently. Had p0101 pop up for a little but but is a new map sensor. I replaced pvc valve and it ran like new but slowly misfire came back then last week took right side valve cover off and ran it and misfire went away and ran nice. Put valve cover on and ran like a champ for a couple miles then slowly developed a p0101 then p0300. Im lost.
Thank you
nice video sir!
would a misfire affect cars ability to shift properly and stop all together to a quiet idle at certain speeds? I have an 86 f150 and usually at about 45 mph after it warms up its act like its sucking too much air and jerk its more pronounced now where it use to be taking foot off gas an reapplying it would cause it, it now does it repeatedly every couple of seconds straight. I'd say like 2 secound intervals for as long as gas is applied and then I have to wait till it drops below 45 to continue driving.
I'm getting a misfire on all 4 cylinders, could this also caused by bad distributor? i only get misfire when i gun it hard. 2000 honda prelude