Hi, i have a '96 W202 C280. After starting the engine and when the engine begins to get hot, the idle goes up and down. The engine is revving on its own. The idle becomes worse when the engine is hot, and a black smoke will come out from the exhaust. There is no check engine light yet on the intsrument cluster. Sometime the engine will stall. I have replaced the fuel filter, cleaned the throttle body yet the problem remains. Help!!

 

Hello! I suspect MAF...

 

but when i'm cruising, everything is fine. but when i have to stop or i'm in traffic, the engine revs on its own sometime hitting high of 1500rpm and as low as 600rpm.

 

Did you ever get to find the cause of this fault? I have something similar on my car.

 

Try replacing the Cam Shaft Sensor, although I didn't have the same exact issue it did make a difference for me and the sensor is easy to get to.

https://mercedesforum.com/forum/mercedes-c-class-10/98-c230-rough-idle-4019/

 

Hey mike, I was just reading your post about your problem being solved with replacing the cam shaft sensor. I have the EXACT problem right now on my 1999 c230 Komp. I even replaced the whole engine and the problem continued. I just wanted to double check that it was the cam shaft sensor and not the crank shaft sensor. Thanks a lot. You can email me back at famofdemers@comcast.net Mike