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

[brock]

Re: Misfire Stumble - Won't Rev

I have not done any troubleshooting at this point. I will check the cap/rotor/dustcap components. They were replaced in early 2015 along with spark plugs and plug wires.

The harness was replaced a couple years ago.

Thanks for the info. I'll take a look and share my findings.

 

[s4cruiser]

Re: Misfire Stumble - Won't Rev

Trans O/L switch has nothing to do with this problem. The O/L switch, if defective, can cause weird full-throttle upshift behavior but that's about it.

The misfire is most likely related to caps/rotors, particularly the insulator behind the rotor bracket - search the forum for details. This will not trigger any codes on any modules, btw. I'm assuming you have checked the spark plugs and they are recent/clean non-resistor F8DC4 (or equivalent from NGK/etc); and the upper wiring harness is not original. The fact that the problem occurred after being parked for 2 months makes me strongly suspect the fluid-on-the-insulator issue discussed elsewhere. I had the identical issue on one of my cars and it would only act up after being parked for 2+ weeks... drive it daily and it was fine.

My car does the same thing even with newer parts (<12 months and not even 500 miles...yeah I don't drive it much).

If I don't drive it for 3 weeks or so then I might as well pull these parts, clean and reinstall. Kinda a PITA but at least it's a simple fix

 

[gsxr]

Re: Misfire Stumble - Won't Rev

99% of the time, people only replace the cap & rotor.

1% - if that many - pull the insulator behind the rotor bracket for inspection, and even then many don't know what to look for.

Replacing the insulator on my car permanently cured this specific issue; however make sure you troubleshoot before throwing parts at it. Keep in mind that per the other threads, new caps & rotors seem to fix the problem for a short time, then it comes back again... making it seem like the caps/rotors are defective, when they are usually fine.




NOTE: Merged threads on same topic.

 

[quicksilver500]

I have and had the same issue. I found spraying about a 1/4 bottle of throttle body cleaner through the intake cleared it up.

 

[Christian_K]

Re: Misfire Stumble - Won't Rev

The O/L switch, if defective, can cause weird full-throttle upshift behavior but that's about it.

Not true. If the switch is defective by constantly closed, it will retard ignition constantly. The introduction into service manual did state this IIRC.

The issue described at the end, is most likely moisture inside the caps. A very long and well known issue on the M119s. When they are not driven for a couple of days they start acting up mostly when fully warmed up. Solution is often to let it run (if the missfires are not severe) for 30minutes or longer and/or take it our for a ride.
However i heard often when caps/rotors are already a bit on the worn side, the engines might stall while driving.
I dont know if these issues only happen with aftermarket caps/rotors. The factory Caps have a electrical insulator coating applied over the bare plastics. Bernard favours the factory caps/rotors and said he cured many issues with them, caused even by Bosch Aftermarket caps/rotors.
I Have painted the rear insulator caps with 2-3 layers of acrylic paint (was advertised as electrical insulator for PCBs) and this permanently cured the short hiccup my car had every 30seconds or so.

 

[gsxr]

Re: Misfire Stumble - Won't Rev

Not true. If the switch is defective by constantly closed, it will retard ignition constantly. The introduction into service manual did state this IIRC.

Brock's specific issue in post #42 indicated the DTC/error code was for the O/L switch not closing, which can cause the WOT upshift problem I mentioned.

I am not sure what the exact symptoms are if the switch (or wiring) is constantly closed; but the FSM indicates that the system defaults into a "fixed operating mode" or "emergency running mode" when a fault is detected. I am not sure if the EZL will retard ignition constantly.

 

[psportoveloce]

Ye olde M119 misfire problem, psportoveloce installation:

After not driving my car for between 2 and 3 weeks, I drove it Sunday 5 min to the grocery store, shopped for 20-30 min, then drove another 10-15 min to the auto parts store. En route to the auto parts store, there was a rapid progression (inside 5 min) from a slight drop in RPM while idling at a light (a very quick miss) to full on "not running on all 8 cylinders/this thing sounds like a horrible jalopy/and doesn't have enough power to make up a hill in 2nd gear at 20mph even at heavy throttle application). While this was happening, it would for a few seconds revert to running (and sounding) like a full strength V8 again, and then quickly revert to its crippled self.

I went inside, bought some wiper blades and other stuff, returned to the car, and it continued to run poorly as I nursed it home the 10 min drive.

I cursed, went upstairs, returned to the car a few hours later and started it in the garage and it ran normally, but I did not drive it.

It's now Thursday and I just finished installing new caps, rotors, and insulators. The old caps and rotors looked used but not horrible; backs of insulators looked pristine til I touched them and detected a film, very thin (about the appearance and feel of a fogged up window, see photo). No measles, no dust on left one (slight orange dust on back of right one including in the recess in the head, one photo of each side attached) and once wiped up, they looked new. On the inside of the caps, I noted a fine coating (looks about like a fine mist of oil that has then had dust exposed to it, which adhered to the oil spray). Spark plugs are Bosch F8DC4 installed by Leistung in 4 months/1200 miiles ago.

My question is this: how do I assess if the problem is fixed? Wait another week and repeat the same duty cycle that precipitated the problem in the first place? Other suggestions? Generally, my standard use pattern for the W124 is to take it on 60+ mile drives every few weeks but would rather not jump back into that use pattern immediately if the car could end up completely debilitated/not running on all 8 a long way from home.

Thanks M119 gurus.

 

[nocfn]

I think it is unlikely to happen with new insulators. The driving pattern described is the issue or at least a major contributor as the car sits and then gets to temp for short drives, and slight condensate of oily vapor from cam seal remains. picture glass of soda sweating in the warm summer out doors. If you run the car for 25-30 minutes at temp then park I understand that is favorable to the short trips, then a week or so off.

I just finished the job but my quest was purely to replace the 1994 original insulators, and my rotor bolts were stripped by the shop who did the rotors and caps. I had this condition of idle once at Christmas, but Houston spring are 85F and 20% humidity so working in the garage on tedious projects like stripped 3mm bolt heads is best done now.

 

[gsxr]

My question is this: how do I assess if the problem is fixed? Wait another week and repeat the same duty cycle that precipitated the problem in the first place? Other suggestions? Generally, my standard use pattern for the W124 is to take it on 60+ mile drives every few weeks but would rather not jump back into that use pattern immediately if the car could end up completely debilitated/not running on all 8 a long way from home.

I agree with nocfn. With new insulators (and caps/rotors as a bonus) the problem is very likely cured. If you are worried about being far from home when it acts up, wait a week or more and go for a shorter drive closer to home. The issue generally occurs shortly after the engine has fully warmed up, after the cold-start enrichment has ended. With the new parts installed, I would be shocked if the problem recurred.

 

[Russell R Coe]

Absolutely second what GSXR has stated many times before.
I had the same issues, and farted around with trying other fixes until I forced my Indy to replace the insulators, and the problem was immediately solved.

 

[500AMM]

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

 

[Gmach]

Re: 1995 E420 coughs stutters & backfires

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

 

[nocfn]

You removed the insulators?

 

[gsxr]

You removed the insulators?

+1... did you remove/inspect the insulators (or, replace with new)...?

:?:

 

[Gmach]

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 :?

 

[r44raven]

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?

 

[tuttebenne]

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?

 

[gsxr]

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.

 

[Gmach]

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.

 

[Gmach]

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.

 

[gsxr]

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.

 

[Gmach]

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.

 

[Gmach]

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.

 

[cole67]

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.

 

[gsxr]

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.

 

[Gmach]

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?

 

[Russell R Coe]

Have you replaced the insulators?

 

[gsxr]

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.

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.

 

[Trae]

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

 

[Stevester 500E]

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?

 

[Trae]

That would be too easy. . . I will try that first.
Thanks!

 

[gerryvz]

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: http://www.500eboard.com/forums/showthread.php?t=5455

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: http://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

 

[quicksilver500]

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

 

[Trae]

Thanks, I will look into this when I can.

 

[gsxr]

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.

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.

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.

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.

 

[nocfn]

I vote EHA 1/8-1/4 turn CW

 

[Gmach]

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.

 

[gsxr]

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

 

[bryanjchen]

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.

 

[Gmach]

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!

 

[Gmach]

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.

 

[gsxr]

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.

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...

 

[Gmach]

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

 

[Gmach]

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

 

[gsxr]

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.

 

[masterolsen]

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-spray-bensinfast-klarlakk-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).

 

[TerryA]

Arnt,

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

 

[masterolsen]

Arnt,

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

Translation: "Petrol-resistant clear coat"

 

[Taxi Driver]

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...........

 

[JC220]

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.