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Thread: M119 engine coughs, stutters, backfires, won't rev

  1. #61
    E500E explorer 500AMM's Avatar
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    Re: M119 engine coughs, stutters, backfires, won't rev

    The never ending "moisted caps syndrome" which may lead to other scenarios as well, has been discussed in the following thread too:

    http://www.500eboard.com/forums/showthread.php?t=4559


    Arnt
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  2. #62

    Re: 1995 E420 coughs stutters & backfires

    Quote Originally Posted by maplevalleyhammer View Post
    Update!
    Turns out that my problem was actually a CPS, Crank Position Sensor!
    Hope you're still on the forum.
    Did you have a code for the CPS ?
    How did you finally end up diagnosing it as the problem?
    I have pretty much the exact same issue but no codes...NONE.
    Been over every part of the ignition system as suggested.
    Thanks

  3. #63
    E500 n00b nocfn's Avatar
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    Re: M119 engine coughs, stutters, backfires, won't rev

    You removed the insulators?
    1994 E500
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  5. #64
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by nocfn View Post
    You removed the insulators?
    +1... did you remove/inspect the insulators (or, replace with new)...?


  6. #65

    Re: M119 engine coughs, stutters, backfires, won't rev

    I removed them and cleaned them and looked for cracks or burn marks.
    Couldn't see anything that didn't look normal. I have a spare set I can swap in and try.
    But they "looked" fine.
    This problem is definitely heat related.
    It starts and purrrs at idle...but after 10 minutes it starts to miss...very subtle at first, just a few small hiccups that gradually get worse to the point that the car will barely idle and eventually it dies and won't start....until it cools down...then it starts right up and purrrs.
    But while cranking it trying to re-start when it stalls hot, it can back fire through the intake.
    Let it cool down and it starts right up and the whole scenario starts all over again.
    To-day, as it was about to die there was a very strong "rotten egg" smell..very strong.
    There is raw fuel getting into the cat.
    So, there is fuel but no ignition...at least not timed ignition.
    I'm hoping it is a bad crank position sensor but oddly, I don't get a CPS code.
    Actually, I get no codes at all....just one flash on all the pins I test.
    This has been a slowly developing issue over the last year.
    It would run fine for a week or two then suddenly I would get one or two small misses at a stop light while trying to move away. It would start to run normally as soon as the RPM got up to 1500 - 2000. but as soon as I came to an idle it will miss and spit and shake.
    I have changed the MAF, ignition module, caps and it would seem to be fixed, for a week or so, then the whole scenario would start again.
    Funny thing is I could have cut and pasted others stories about their experience with this issue with this engine and saved myself the writing....it's so similar.
    The frustrating thing is that nobody posts their conclusions or what they discovered to solve the problem. Of course that assumes they solved the problem
    Last edited by Gmach; 3 Weeks Ago at 09:47 PM.

  7. #66
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Have you tried 500AMM's trick of cutting extra ventilation slots in the distributor caps to aid ventilation?

    See here: http://www.500eboard.com/forums/showthread.php?t=4559. Post #47.

    I had exactly your symptoms, experiences. The back sides of the insulators proved to be completely clean, while the front sides had just a very, very fine (almost indiscernible) "misting" of a substance which could have been a mixture of oil/water.

    Thorough cleaning, plus Arnt's ventilation modification, has ensured no further problems.

    Having said all that, my experience would indicate E500Es don't seem to like short journeys. Far better to give them a good blast when you take them out, rather than do a short school run and park it back in the garage?

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  9. #67
    Junior Member tuttebenne's Avatar
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    Re: M119 engine coughs, stutters, backfires, won't rev

    FWIW, I had similar symptoms (post cold start miss/low RPM/farting) after the car sat for a few days. Gradually, if the car was left running in this sorry state, it would finally clean itself up. If the car was used daily, no problem; but if it sat for a week - oh man, you could almost predict when it would happen. The last thing I did was pull the EGR and clean it up. It (the EGR) was sluggish when removed but snappy after clean up. Believe me; if the car still had the original problem, my wife would have let me know. Make any sense to you gurus? Could the EGR being stuck cause these symptoms?
    Andy

  10. #68
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Gmach and tuttebenne... scroll up and read post #6 and #17 again.

    Gmach, your symptoms indicate a misfire problem. The insulators can look fine and not perform fine.

    There are multiple different threads on this subject and some people do not post an update as to what (if anything) fixed their problem, but others have posted that given the specific symptoms discussed, replacing the insulators usually cures the problem. I reported this in post #53 above for my car.


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  12. #69

    Re: M119 engine coughs, stutters, backfires, won't rev

    Ok....thanks. I tried to put the SL's CPS in but the screw hole is just off a bit. Enough so that the screw won't go in.

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  14. #70

    Re: M119 engine coughs, stutters, backfires, won't rev

    To-day I installed the new crank position sensor with no change. Car starts and runs like a dream but as soon as it warms up, after a mile or so, it starts to miss and eventually stalls then will not start. Let it cool down and it starts right up and runs....for about a mile.
    I'll keep looking...frustrated that there are no codes at all.
    What sensors are critical to ignition?
    I am getting lots of fuel based on the smell from the exhaust but I think the plugs are firing randomly based on the backfire up through the MAF /intact.
    A sensor is getting hot and malfunctioning...but which one and why aren't I GETTING A CODE? Not even for the misfire...if that is what it is.
    Last edited by Gmach; 2 Weeks Ago at 09:31 PM.

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  16. #71
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    Re: M119 engine coughs, stutters, backfires, won't rev

    If you haven't swapped in the spare insulators yet, I'd try that next.

    Ignition misfires almost never trigger a fault code unless a particular cylinder is not firing at all, for an extended period. Misfires also tend to cause unusual exhaust odor.


  17. #72

    Re: M119 engine coughs, stutters, backfires, won't rev

    Yeah...that'll be next. It's just that there is NO indication, visually, that they are bad. No cracks or burn marks. And if only one was bad why would the car completely stall and not re-start. I suppose both could be bad but again I see no indication.
    Thing is this problem has been document on this and other forums at great length. The descriptions given by completely different individuals on different forums is exactly the same..misfire / backfire / then stalls and won't re-start but only when hot..maybe 10 minutes or 1 mile after starting cold.
    So this is a common repeating problem yet nobody re-posts what they found and how they solved the problem.....because it will be the same for all of us with this issue.
    Isn't that what a forum is for....to share the knowledge....rather that just leach.
    I just hate throwing money at this in the "hope" it will get fixed.

  18. #73

    Re: M119 engine coughs, stutters, backfires, won't rev

    UPDATE.....replaced the crank position sensor with a new Bosch and it didn't completely solve the issue.

    I did notice that I could create the problem or at least make it worse, if I started to mess around with the cable coming from the throttle body. So I thought I would take it out and give it a good cleaning and look at the throttle position sensor.... but.... before I did that I swapped my MAF.....problem has gone away! Runs like it should...no miss, hesitation, backfire, foul smelling gas...all gone! Didn't have to remove the throttle body! I've ventured around town without issue and am getting more and more confident that it has been fixed.

    Unfortunately NONE of the several times that I read the DTC did it ever show either the CPS or MAF (or anything else for that matter).....explain that if you can. I also thought that a bad MAF would have the car surging at idle but not completely die or act like it was running on 2 cylinders with bad timing so I never considered the MAF So all the signs that pointed to ignition were wrong!

    I sure hope I haven't jinxed myself by posting this as a "fix" but I thought it might help someone else.

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  20. #74
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Was having the same problems with misfire and stumbling after prolonged down time. Finally got the time to check my caps, rotors, and insulators. All were wet and required cleaning. Going to replace insulators, caps and rotors are new although one rotor had stripped allens. Used a 5/16 to 7/16 extractor to remove the three screws. Worked like a dream! The yellow painted part # on one of the insulators was interesting. Probably original...not sure.
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  22. #75
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by Gmach View Post
    Unfortunately NONE of the several times that I read the DTC did it ever show either the CPS or MAF (or anything else for that matter).....explain that if you can. I also thought that a bad MAF would have the car surging at idle but not completely die or act like it was running on 2 cylinders with bad timing so I never considered the MAF So all the signs that pointed to ignition were wrong!

    I sure hope I haven't jinxed myself by posting this as a "fix" but I thought it might help someone else.
    Great to hear you nailed down the problem. I don't believe the MAF will not trigger a DTC (error code) unless the computers cannot talk to it, i.e. it's disconnected or has a wiring problem. This means it can provide false readings (more or less air than actual) which can cause all sorts of weirdness, with no codes. This has been reported several times in the past, but IIRC, never with symptoms which mimic the "misfire and stumbling after prolonged down time". Generally, the MAF can be diagnosed via a digital scanner that shows the live data airflow readings; a good tech will recognize if the readings are abnormal at various RPM.

    The usual CPS failure symptoms do not include misfiring, it's generally stalling and/or refusal to start, but again may not trigger a code. Both the MAF and CPS failures are much less common, IMO, than the caps/insulators. I'm fairly confident that Cole's issue in the above post will be cured with new insulators, his pics show the classic 'fluid on the back' problem.


  23. #76

    Re: M119 engine coughs, stutters, backfires, won't rev

    It's back...sorta!
    Been running fine for the last couple of weeks and I was starting to trust it again.... until to-day!
    Now when I try to accelerate away from a light, if I apply too much throttle, it just bogs down with a real deep "throatie" sound like it isn't getting enough air. If I back off it returns to normal and stays like that as long as I don't apply too much gas too fast.
    If I slowly apply the gas then it picks up as normal.
    No backfire or bad miss....just this "bogging" down.
    No DTC's.
    Sound familiar to anyone?

  24. #77
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Have you replaced the insulators?

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  26. #78
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by Gmach View Post
    If I slowly apply the gas then it picks up as normal. No backfire or bad miss....just this "bogging" down. No DTC's. Sound familiar to anyone?
    Those specific symptoms sound like what I experienced with a failing fuel pump. Driving with a fuel gauge visible from the driver seat pinpointed the issue, the bogging down correlated directly to when fuel pressure would drop. May not be what you are dealing with, but at least it can be diagnosed with the proper tools.


    Quote Originally Posted by Russell R Coe View Post
    Have you replaced the insulators?
    ^^^ +1. I never saw confirmation either way. If the car is having issues and the insulators are original, it's worth the $100/pair for new Bosch as preventive maintenance.


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  28. #79
    E500E Guru Trae's Avatar
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Going to check fuel pumps on my M117 as I have similar symptoms if I floor it from a stop.
    almost like turbo lag.
    Trae
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  29. #80

    Re: M119 engine coughs, stutters, backfires, won't rev

    Any chance it could be a bad fuel pressure regulator?
    Quote Originally Posted by gsxr View Post
    Those specific symptoms sound like what I experienced with a failing fuel pump. Driving with a fuel gauge visible from the driver seat pinpointed the issue, the bogging down correlated directly to when fuel pressure would drop. May not be what you are dealing with, but at least it can be diagnosed with the proper tools.



    ^^^ +1. I never saw confirmation either way. If the car is having issues and the insulators are original, it's worth the $100/pair for new Bosch as preventive maintenance.


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