Michael Pietrzy

97 e 420 4.2 Engine was running great than this morning when i got on the x way started running rough like it wasn't running on all 8. CEL came on and
Eletronic senser came on. After cool down started fine but when warmed up same problem?

Thanks

F1Fan

I had a similar issue in another car. When cold, everything would run fine. However once warmed up, it started to misfire. Found out that one of the ignition wires had deteriorated so there was not enough electrical current reaching the spark plug, which resulted in a misfire. The car felt horrible when it happened. Hope this helps. Might be a good idea to get the error code diagnosed first.

MB Enthusiast

I had the same problem and it was a spark plug. I replaced them all and the ingnition wires as well. The bosch plus model plugs were recommeneded and the Beru wire set.The car runs great now.

Michael Pietrzy

Going to get a code reader will go from there
let you know
thanks

Michael Pietrzy

Checked the spark plugs first and found water in 3 of the spark plug wells blew them out checked all plugs back together and running great again. Water must have gotten in when cleaning engine. Cleaned before never had problem, will have to get new seal for covers over plug covers
so Thanks Again for help :

E-Klasse

If you would have said that you washed it, I would have said to check for water in the spark plug wells. When I had my car detailed and they flooded my spark plug wells and did not blow the water out. It ran rough and the CEL came on for cyl. misfire. Glad to hear you solved it.