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

  1. #61
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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:

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


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

    You removed the insulators?
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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; 05-02-2017 at 10:47 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: https://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
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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; 05-08-2017 at 10:31 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
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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.
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  29. #80

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

    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.
    Any chance it could be a bad fuel pressure regulator?

  30. #81
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    Re: M119 engine coughs, stutters, backfires, won't rev

    That would be too easy. . . I will try that first.
    Thanks!
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Note that on an M117, the fuel pressure regulator (called the "diaphragm pressure regulator") is underhood between the cylinder banks, and is of a very different design than the one on the E500E/M119/LH system. It's much larger and more expensive (several hundred dollars to buy one new, last time I checked). They only go out on the M117 with some rarity.

    It's a very different thing than on the M119 and a bit more difficult to replace, because it's plumbed directly into the fuel system, rather than sitting on a fuel rail.

    If fuel pressure is an issue, I'd recommend doing a fuel pressure leakdown test before throwing parts at things. This will test the system and determine whether there is an issue with the components (and there are several for both the M117 and M119) that maintain and regulate fuel pressure.

    For the M119 and M104 specifically, there is a HOW-TO on measuring fuel pressure. It can be found here: https://www.500eboard.com/forums/showthread.php?t=5455


    Quote Originally Posted by Trae View Post
    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:

    What I have found with the M117, where there is a stumbling when the throttle is floored quickly, is that an adjustment of the EHA is required to slightly richen the mixture. More on this here: https://www.500eboard.com/forums/showthread.php?t=2759

    Note my paragraph:
    "For small issues, however, you can make small adjustments perhaps without the need for the fuel pressure measurement. I was having a small (but certainly noticeable) stumble in my 560SEL from a stoplight or stop sign upon SUDDEN/RAPID acceleration. Regular/smooth acceleration was just fine. I had a phone discussion with Jono a few weeks ago, and he suggested adjusting the EHA to richen things up a bit, as the 560 M117s are set to run quite lean from the factory. Often, richening up things a bit can dramatically help low-speed acceleration feel, as well as hesitation/stumbling problems when taking off from a stop. So, I decided to follow Jono's advice and adjust my EHA to richen things up to eliminate the hesitation from sudden throttle application from a standing stop."
    Cheers,
    Gerry

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  33. #83
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    Re: M119 engine coughs, stutters, backfires, won't rev

    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.

    Dave,

    I had the same issue, both our cars run fine cold. I have mine in nearly the same state as Gmach, but my off the line stumble occurs above 1/2 throttle, only when hot (~85C+). Idle is decent with only some hickups, I just repaired my DAS R-whatever to Rs232 converter cable and will check live values if it is actually fixed (bad solder joints).

    I had some old insulators from my 92' that I put in they were orange, and the ones on the car were black. It seems like one would just need to replace the o-ring, how do the insulators fail? The black ones had rock solid o-rings, and the orange ones had soft foam o-rings. They are only a moisture barrier right? The insulation is in the rotor.

    Parts swapping did nothing for me, only carb cleaner made a difference.

    -Mike
    Last edited by quicksilver500; 05-25-2017 at 06:49 AM.
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  34. #84
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Thanks, I will look into this when I can.
    Trae
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by Trae View Post
    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, as Gerry noted, the M117 is totally different. I would suspect an EHA adjustment may help but I really do not know the CIS systems very well.


    Quote Originally Posted by Stevester 500E View Post
    Any chance it could be a bad fuel pressure regulator?
    Very unlikely, but I suppose it's possible. The regulator would have some somehow stick in an open position to reduce pressure far below normal limits. I've never seen this personally. The typical FPR issues tend to be hard starting (when hot?) and leaking out the diaphragm. LH FPR's are cheap and easy to replace, if it's old / original, probably worth the $40 as preventive maintenance.



    Quote Originally Posted by quicksilver500 View Post
    I had the same issue, both our cars run fine cold. I have mine in nearly the same state as Gmach, but my off the line stumble occurs above 1/2 throttle, only when hot (~85C+). Idle is decent with only some hickups, I just repaired my DAS R-whatever to Rs232 converter cable and will check live values if it is actually fixed (bad solder joints).
    The low fuel pressure thing causes a smooth power loss. On my car it was intermittent and would typically occur when the pumps were fully warm, i.e.after 15+ minutes of driving. It would idle ok but on takeoff when you want power, there isn't enough fuel available and it acts like a wimpy 4-cylinder. Watching the gauge you can see pressure drop from ~50psi down to ~20 under load. When the intermittent pump came back to life, pressure would snap back to 50psi and power would come back to normal. Really weird. No misfiring, no codes, just severe power loss at anything more than very light throttle.



    Quote Originally Posted by quicksilver500 View Post
    I had some old insulators from my 92' that I put in they were orange, and the ones on the car were black. It seems like one would just need to replace the o-ring, how do the insulators fail? The black ones had rock solid o-rings, and the orange ones had soft foam o-rings. They are only a moisture barrier right? The insulation is in the rotor.
    The orange insulators are Bosch, and black are Doduco (NLA). I believe the O-ring is present primarily as a dust and moisture barrier and generally has minimal effect on ignition performance. I don't think anyone fully understands exactly why the old insulators fail to, uh, insulate... but Klink's theory in post #6 covers it fairly well.


    To reiterate from post #17: The insulator failures I've experienced follow this specific scenario: Car must sit for at least 1 week, then start and drive for ~10 miles, shut engine off for 5-10 minutes, try to restart, result is severe misfire and/or a no-start condition. Wait 30 minutes, car starts immediately and runs flawlessly for days/weeks/months, and continues to run perfectly... until it is parked for at least 1 week, then the scenario above reoccurs.

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  36. #86
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    Re: M119 engine coughs, stutters, backfires, won't rev

    I vote EHA 1/8-1/4 turn CW
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  37. #87

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

    I've been trying for sometime to find a smoking gun with regards to an engine that runs great when cold but as soon as it gets hot it misses and shakes and runs like crap then dies. NO CODES....bear in mind the OBD1 systems is marginal at best. Anyway, turned out to be the left coil. Go figure...how could that not set a code? Test your coils if you have a similar problem...when HOT. When it starts acting up pull the coil wire on one distributor then try and start it. If it runs crappy then plug that back on and try the other. If the car won't start...that's the bad one and probably the source of THAT problem.

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

    Did you replace just the one coil, or both? Has that permanently solved the problem?


  39. #89
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Noticed that my car would start fine on cold start, but after a little while driving would start to stutter and shake, have a hard time accelerating, though after driving a little, problems would seem to go away. Recently, the problem has gotten progressively worse and in addition to above issues, car would at times stall, not start and backfire. Went to my mechanic and saw this thread so pinpointed the issue fairly quickly and now ordering the parts from the US as they are not in stock in Taiwan. The dust shield looked like it had gotten a case of the measles and the distributor cap was very damp. Ordering the distributor caps and rotors along with the distributor dust shield now. My air filter and spark plugs needed a changing also so have been switched out, so hopefully all issues will be resolved shortly. Will report back shortly. Weather in Taiwan is quite similar to Miami, is this one of the causes for the moisture in these parts? Or is it also a result of me not driving the car that often, maybe only a few times a month on the weekends.
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  41. #90

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

    Removed and replaced. It has to be something else....and the exact same issue plagues many owners of 124 owners with this engine.
    But no smoking gun...at least not posted!

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  43. #91

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

    Quote Originally Posted by gsxr View Post
    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.

    If the ignition module fires the coils....what controls the ignition module?
    I've put three different EZL (ignition modules) in this car with basically the same result.

    It seems that if I start the car cold it will run fine until I turn it off.....allow it to heat soak.....then it won't start.
    I have a feeling, (although I'm not game to try it) the car will drive without issue, at highway speed, for ever.
    But that is just a guess because it doesn't miss or spit at lights any more...at least not since I changed the coil.
    Then pattern of failure has changed....but it still fails
    Start cold and drive >no problem.
    Turn the car off when hot and let stand for 5-10 minutes > it will not start. It tries to but just back fires.
    Let it sit for 1/2 an hour or so> starts right up and idles as if it was a new car.

    I ordered the insulators for the distributors to-day. Mine are fine (at least they look fine) but why not try it.

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  45. #92
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by Gmach View Post
    If the ignition module fires the coils....what controls the ignition module?
    I've put three different EZL (ignition modules) in this car with basically the same result.
    The ignition module (EZL) is the computer which controls all ignition functions. It gets inputs from various temp sensors and from other modules via CAN. The EZL usually either works or it doesn't, I've never heard of one misbehaving intermittently based on temperature or anything else.


    Quote Originally Posted by Gmach View Post
    It seems that if I start the car cold it will run fine until I turn it off.....allow it to heat soak.....then it won't start.
    I have a feeling, (although I'm not game to try it) the car will drive without issue, at highway speed, for ever.
    But that is just a guess because it doesn't miss or spit at lights any more...at least not since I changed the coil.
    Then pattern of failure has changed....but it still fails
    Start cold and drive >no problem.
    Turn the car off when hot and let stand for 5-10 minutes > it will not start. It tries to but just back fires.
    Let it sit for 1/2 an hour or so> starts right up and idles as if it was a new car.

    I ordered the insulators for the distributors to-day. Mine are fine (at least they look fine) but why not try it.
    What you describe above is almost textbook for the "bad insulator" syndrome. I am very curious to hear what happens when you receive new ones and install them...


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  47. #93

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

    I will be amazed if it is the insulators....but I am ready to be amazed.

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  49. #94

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

    Could there be a problem with the CAN itself that is heat related and doesn't throw a code? Which module is the CAN?

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

    Quote Originally Posted by Gmach View Post
    Could there be a problem with the CAN itself that is heat related and doesn't throw a code? Which module is the CAN?
    CAN = Controller Area Network. It is a serial communication bus that passes data between the modules. It is not a module itself; each module (LH, E-GAS, EZL, etc) has the CAN functionality built in, and they all connect via a shielded pair of wires. If you are familiar with computer networking, think of CAN like Ethernet... two or more computers each have network capability, and are connected by wires to pass data between them. Same basic concept for the Mercedes computer modules.

    Anyway - if the CAN is acting up, there should be error codes stored on multiple modules, each complaining about lack of CAN transmission or reception from a particular other module. It is extremely unlikely you are experiencing a CAN issue.


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

    My engine M119.972, 500SL 1993
    Problem: Moisture in caps/insulators
    I have had this problem with caps and insulators, 2 years ago I did this and the problem went away.
    What I did was that I coated the insulators and caps with this https://megaflis.no/nordsjo-decomax-...akk-400ml.html its in Norwegian. In English, "Petrol-resistant clear coat".
    Baked it in the oven on 60 degrees celcius for an hour, let it cure for a week and ordered original rotors. Caps were Bremi and insulators were Bosch.
    No more moisture for me, problem solved(for me anyway).
    Last edited by masterolsen; 07-19-2017 at 07:17 AM.

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

    Arnt,

    We need a translation. What is this stuff? I would think everybody in Norway would want this stuff.
    Terry

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

    Quote Originally Posted by TerryA View Post
    Arnt,

    We need a translation. What is this stuff? I would think everybody in Norway would want this stuff.
    Translation: "Petrol-resistant clear coat"

  56. #99
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by TerryA View Post
    Arnt,

    We need a translation. What is this stuff? I would think everybody in Norway would want this stuff.
    Oh, nothing more or less, than a clearcoat only that it says petrol safe or steadfast, anyway it wouldn't help if the Caps are shot interally.

    That I reacently experienced, the Beru caps I have had some time, worked just fine and looked very, almost new inside BUT when the
    motor had been driven varm/hot for some 20min. at hard acceleration round 140km/h several times it felt like almost starvation!

    A slight feel of a disturbed idle and when at a red light in gear,I had to selekt N, I have been through this Before and it was SO VERY
    obvious, DAMN them Distr.caps. Back home, a change to the used Bremi Caps&rotors, What do you Think.....Sweet as Tupelo Honney

    Now I ordered new items from not MB but a parts dealer here, BOSCH delivered, must be same as oem but some 200+ € less with
    my discount. Not taking any more risk, buying from internet anymore...........
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  57. #100
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by Gmach View Post
    I will be amazed if it is the insulators....but I am ready to be amazed.
    Am I correct in thinking this issue is also being discussed on another forum as below?-

    http://www.benzworld.org/forums/w124-e-ce-d-td-class/2853426-400e-dies-when-gets-hot-still.html

    Maybe this is not you – but the posts seem to relate. Maybe you could take a couple of minutes to fill out your profile on 500E board.

    For completion of the query on here some of the posts might prove useful. The information on there suggests used insulator discs were fitted. I agree with GSXR that your case sounds like classic failing insulators.
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  59. #101
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Quote Originally Posted by Taxi Driver View Post
    That I reacently experienced, the Beru caps I have had some time, worked just fine and looked very, almost new inside BUT when the
    motor had been driven varm/hot for some 20min. at hard acceleration round 140km/h several times it felt like almost starvation!

    A slight feel of a disturbed idle and when at a red light in gear,I had to selekt N, I have been through this Before and it was SO VERY
    obvious, DAMN them Distr.caps. Back home, a change to the used Bremi Caps&rotors, What do you Think.....Sweet as Tupelo Honney

    Now I ordered new items from not MB but a parts dealer here, BOSCH delivered, must be same as oem but some 200+ € less with
    my discount. Not taking any more risk, buying from internet anymore...........
    I hate to rain on your parade, but this has been discussed multiple times... bad insulators cause a misfire which is "cured" by different caps and/or rotors. Until the same thing happens again a few months later, with the "new" caps/rotors. And then new caps/rotors cure the problem... until it happens again, and again. I wouldn't be so quick to bash on the Beru caps as the problem. Also, I've personally had a defective brand-new Bosch cap, straight out of the box (again, I'd posted this multiple times) which caused a misfire at hot idle. Bosch is not necessarily any better. And Bremi is not OEM for any M119 ignition parts.

    So. Do you have new insulators in this engine? And how many miles were on the "defective" Beru caps?


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

    Quote Originally Posted by JC220 View Post
    Am I correct in thinking this issue is also being discussed on another forum as below?-

    http://www.benzworld.org/forums/w124-e-ce-d-td-class/2853426-400e-dies-when-gets-hot-still.html
    Yes, I believe they are the same person / car.


    Quote Originally Posted by JC220 View Post
    Maybe this is not you – but the posts seem to relate. Maybe you could take a couple of minutes to fill out your profile on 500E board.
    +eleventybillion, for every forum member. I wish we could make location and vehicle info required fields during registration.


    Quote Originally Posted by JC220 View Post
    For completion of the query on here some of the posts might prove useful. The information on there suggests used insulator discs were fitted. I agree with GSXR that your case sounds like classic failing insulators.
    That's my understanding too, used parts were fitted, but new ones MAY be on the way.


  61. #103
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    Re: M119 engine coughs, stutters, backfires, won't rev

    I'd posted this multiple times) which caused a misfire at hot idle. Bosch is not necessarily any better. And Bremi is not OEM for any M119 ignition parts.

    I hate to rain on your parade, but this has been discussed multiple times... bad insulators cause a misfire which is "cured" by different caps and/or rotors

    The Bremi, who said it was oem? I had a set used, and they cured the problem for now, new BOSCH on the way, and not via ebay, so they are for sure BOSCH!

    The insulator, what does it do exept keeping out mostly staubschuts or dustcover and moisture/dampness? there is no high tension voltage below the rotor
    if the spark goes the right way, when humidity gets in there, the cover does not seem to do it's job there, spark takes it's easiest way in there....

    I do not really know for sure, but mentioned clear coat on a cleaned dustcover, inside, would that not do the same "job" as a new one?

    The caps, do not look too bad, same with the rotors, I guess the resistance inside Changes at high temp? Maybe it burns out and forces
    the spark to jump within the resistor, I should open one cap and see. You can not judge the condition of a cap just by looking at the Surface.

    So much have I learnt, maybe I should get the E50 ready and not Think of the caps, anyway, allthough more complex, the ign. issue is not there.
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Hi. I have an E500 with some 90kkm on it, that I bought a few months ago. The car had been sitting from quite some time, but we did the full recommissioning and service routine, and also changed plugs, rotors, caps, and plug wires. Initially the car worked great, but gradually developed a misfire, like described above. We found the distributor caps were wet inside, and the insulators had measles. On your advice I changed the insulator caps to have all parts new, and the car's running improved tremendously, and there seemed to be more power available. (We did the same thing to my friend's 500E as well.) Well, the joy lasted only about 3 days, before the misfire returned. It's been raining..... Could this be moisure having returned? I will obviously check again, but it seems somewhat strange that a 90s Merc can't take a rainshower...... If there is moisture in there, what do I do (after cleaning and drying things out)? If not, what do I look at next? Has anyone found out more?

  63. #105
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Plug part number and what gap?
    1994 E500
    249/275 - 8F19 or 8F32 or 8320

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

    Will check and revert!

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

    Just want to be sure they are proper fir the car without the R in the number and nothing platinum or fancy, also gapped to approx 1.0

    Also just about the “miss”... torque spec matters on the plugs too, wire resistance bad out if the box. Bad mounts can translate slightest shutter even if the compressor turn on or
    Off. GSXR or Klink are better than me on this...
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    Re: M119 engine coughs, stutters, backfires, won't rev

    Just curious, what brand of caps, rotors, insulators, and wires were installed? Also need to confirm correct plug type / part number although the 'wrong' plugs should not cause a misfire, unless fancy fine-wire plugs were installed (these engines don't like those). With all new parts and correct plugs, it SHOULD be running fine, regardless of weather / humidity / rainshowers. Is the misfire only at idle, or on acceleration, or...?

    BTW, congrats on the recent E500 purchase, and welcome to the forum!


  67. #109
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    Re: M119 engine coughs, stutters, backfires, won't rev

    my E420 had blocked cat and blocked exhuast mufflers from sitting too long and not used. Was not revving and had a very bad idle. Sometimes would not even start.

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