Mercedes-Benz Forum banner

2005 E320 CDI engine misfire at idle when fully warm

678 Views 14 Replies 4 Participants Last post by  DieselBound
I have been pulling my hair out trying to solve this problem. Several months ago I noticed my car would sometimes stumble at idle after a long day of driving. It would only happen for a moment or two and it would smooth out. But as the weeks passed, the problem would happen more frequently with less driving, and eventually turned into a full blown misfire at idle. However the problem only happens at idle when the engine is FULLY warmed. If I let the car sit for a few hours and go to start it, the engine purs just fine....until it warms up again. And it only happens purely at idle and when I let my foot off the accelerator. Any throttle at all and the engine totally smooths out and works perfectly fine.

I have tried replacing the injector nozzles, seals, and return line o-rings with no change to the problem whatsoever. I just got done doing a leak off test and all the fuel levels were dead nuts even with each other.

I have replaced the fuel filter, bypassed the EGR valve, and I have all but deleted the swirl flaps. Nothing has even made a change.

I have taken this car to a mercedes shop to see if there were any hidden codes, and with the exception of the egr being bypassed, there are no codes for fuel pressure.

I honestly have no idea where to go from here. I would appreciate any insight you guys might have.
1 - 2 of 15 Posts
Does it start regen attempt then?
I do not believe the OM648s have a DPF filter and therefore the car should not have done a regen. I am pretty sure DPF started with the OM642, but I could be wrong.
Well, my W211 OM648 had DPF, but it was a initially sold for German markets.

Check what your back pressure sensor reads when problems start. That is very common source of gremlins in OM642. Overall, it could be wise to try any angine live data when it starts misbehave. Problem is little bit chicken - egg dilemma, when some reading jumps, is it culprit or result... Good luck!
1 - 2 of 15 Posts