Car dies and or runs rough after 10-15 min

[88260e]

So Ive posted on this subject before still chasing the same problem??? So my 92 400e for over a year now will randomly act crazy!!! The more it sits the more it seems to happen? After a short drive or sitting at idle the car will buck,stumble,misfire,and sometimes die. If it does die it will not restart unless you weight an hour then it will start up fine an run fine??? The car will go sometimes a month or two without a stumble and sometimes it will happen daily. New this year, rotors, caps, wires, plugs, air filters, last year CPS, FPR, Coils, fuel pump relay, battery, alternator, starter, upper harness. ETA was sent out and bench tested, all vacuum hoses are new all breather hoses are new. The mechanics at the shop I worked at couldn't find the problem, brought it to another shop Master Merc Tech, we thought he found the problem! The ends on the new wires to the coil seemed loose, pressed on but not twisted on so we tightened them and the car seemed fine for a month then it went stupid again??? I'm lost??? someone mentioned to disconnect the aftermarket alarm to see if that helps so going to try that ASAP. But anyone out there run in to this problem before cuz it's driving me crazy. Sorry if you've read other posts about this problem before, and I'm repeating myself but I'm S O L

[tbomachines]

Next time it happens see I the fuel pumps switch on? You've covered all the major bases. Sounds a lot like ovp relay issues but I'm not sure the 400e has one - someone chime in?

[88260e]

Yup no OVP

[Calspeed]

I recently has the EXACT same issues.

I have a 1993 500E that would start fine and run awesome. But after 5 minutes it would stumble but continue to run as if on half an engine. And if I stopped on a hill... Forget it! I would not be able to pull away from the curb because the car had no power to get it moving.

And with a 500E that's horrible as it's programmed to start in 2nd gear. And San Francisco is not short of hills.

After much anguish my mechanic hooked up a pressure gauge and drove it. He found that the pressure dropped after a few minutes of driving.

Replaced the fuel pump and filter and I'm "lighting up" the rear tires again.

You mentioned that you recently changed the pump. Maybe it's the filter?

Good luck bro!

Miguel

[88260e]

Never did the pumps, did the filter 2yrs ago, picked up a used EZL to try will see, checked the CPS seems ok 854 ohms cold. if the EZL don't fix it ill grab some fuel pumps?

[o0norton0o]

Since the car won't restart sometimes when it acts up, you have an opportunity there to do a simple test while you're problem is occurring but you will need to be prepared.

One of the simple tests I do on all the engines I work on when they quit, (lawnmowers, chainsaws, motorcycles, cars...) is a gas starvation test.
I use a small gas can or use a turkey baster for some sidways carburators to give the engine a little shot of gas when it won't start. IF it kicks over, but then dies when it burns up that shot of gas, then I know the problem is fuel delivery related and I don't waste time chasing down ignition related problems. I go after the fuel delivery system components.

My 560 did something similar to what you discribe a few years ago. I would drive somewhere and turn it off to go into a store, then when I went to leave, it wouldn't restart for an hour. I ended up carrying a small gas can (which was smelly) and traced it to fuel delivery issue by the method I described above.

Luckily for me, someone locally was parting out a 560 and I salvaged their whole injector system and rebuilt my whole fuel injection system and replaced the fuel pump relay and it's never been an issue since. I am not sure what exactly the issue was, but I know it was a fuel delivery issue.

If I was you, I would find another working fuel pump relay to carry around and next time the car "boinks" on you, swap the fuel pump relay with the extra one.

[88260e]

Fuel pump relay was changed a year or two ago, but its worth a shot! Tried a Used EZL same problem today I'm going to ray a ECT sensor, starter fluid would do the same thing as carrying gas around right??

[o0norton0o]

I don't like starting fluid. I think it's alcohol based, and it's in an areosol can. I've seen a lawnmower go up in flames from a backfire when someone was using starter fluid. I supose it could work too, I just don't like the stuff. I just carried a small gas can in the trunk well, in a plastic garbage bag. Once I was sure it was fuel delivery related, I salvaged parts and got it fixed. I didn't like carrying a gas can in my mercedes, although I do it in my work Van all the time..

Intermittent problems are the worst. The problem has to happen when you have your tools handy to test things. While the weather is nice, I would leave the car running in the driveway and see if you can get it to bonk there. You'ld have a chance of having all your tools at hand as well as not having to carry a gas can or starter fluid in your car...

[88260e]

Threw the ECT sensor in, same thing, but this time it didn't die so I took it for a twenty minute drive didn't run bad a little rough at idle? Might through a fuel filter at it can't remember if I've changed it!

[kellya1799]

Any luck here. Very same behavior on our 93 400e. It started as rough idle, die after the car was warm. Now, it is a challenge to get it started at all...sounds like it is backfiring initially if we are able to get it to start at all. Nobody in this small town will touch the car.

[daddi]

Condensation in the ignition caps of the M119 engine is very common if they're not used daily, just dry them out and keep trucking.

[neanderthal]

I suspect the fuel pumps as well.

I had a similar problem with my 300E 2.6.

[m00n]

Someone resolve this problem ? The same situation here in w140 500SE 1992. m119.970
When car is cold run perfectly, stable idle, good acceleration no missfire no backfire. When it getting 80C then start to missfire engine shaking and finally dies. After that i cant restart it. Car is crank but backfire to the exhaust so fuel is leaking. I thin i s not fuel pump problem becouse i checked fuel pressure and it was 3.5bar on idle and 4.0 bar while accelerate. I changed almost everythin: CPS, Cam sensor, O2 sensor, 4pin coolant sensor, Used EZL, Caps, Rotors, Fuel pressure regulator, clean injectors, are vaccum and breathing hoses, intake manfiold gaskets, engine/lower wiring harness, Used base module. I think about LH module and MAF. Please any advice can help. the car is using only in weekends but the problem wasnt occured before. I found lot off posts about it its common problem but finally unresolved.

[rayhennig]

Originally Posted by m00n

I changed almost everythin: CPS, Cam sensor, O2 sensor, 4pin coolant sensor, Used EZL, Caps, Rotors, Fuel pressure regulator, clean injectors, are vaccum and breathing hoses, intake manfiold gaskets, engine/lower wiring harness, Used base module. I think about LH module and MAF. Please any advice can help. the car is using only in weekends but the problem wasnt occured before. I found lot off posts about it its common problem but finally unresolved.

Caps, rotors etc. suggest to me the Bosch KE injection and separate ignition. In which case, LH module and (hot) MAF are not there, only a mechanical MAF.

I assume you installed best quality (MB/Beru/Bosch) caps and rotors?

RayH

[m00n]

I changed all ignition from BERU: caps, rotors, 2 coils, wires and plugs.
I have Bosch LH-jetronic fuel system not KE, and i have hot wire MAF. It's w140 with m119.970 engine. My guess is broken ECU (LH module)(solder joints or something) or sometimes i think about broken exhaust valves ... This answer what i get from here:

Everyday Diagnostics: Mercedes S-Class Misfire

Pico: Temperature will affect the performance of High voltage insulation and so your symptom most certainly matches this case study. How does your vehicle perform when cold in terms of load? Can the vehicle be accelerated under WOT with no misfire or backfire? Electrical loading can also highlight poor insulation issues. An insulation tester may also prove if your rotor has suffered an internal failure once at the failed operating temperature. Have you been able to capture the primary and secondary waveforms during cranking as with the above case study? Mechanical issues must also be checked as multiple tight valve clearances (Exhaust) would give you compression failure when hot and of course backfire.