When moderate to heavy acceleration from a stop or crawl, the engine will hesitate a bit and sometimes backfire which I hear from the center of the vehicle. The check engine light came on about the same time as I noticed backfires and hesitation.

I went to an exceptional dealer, Motorwerks in Illinois and they said the engine light was caused by a bad blower unit which supposedly helps with emissions and I did not fix this because he said it ONLY affects emissions and its $1100. The tech could not reproduce the acceleration noise.

Could the blower unit cause this? From what I have read, this seams to be a common issue?

Are there any success stories regarding these symptoms?

Thanks for reading!

 

i think is your air flow meter respone slow and cause the back fire just once ,when it heat up the heater element you dont have this happen.
when you go to the dealer testing ,the car heat up already ,so they cant find the problem....

 

Hello quigley,

I dnt know if you are still facing the problem, but I think and according to the symptoms you are describing, the wiring harnesses need to be replaced. It is a very common problem that occurs to C-Class between 94-96. Accuatly the materials of the wiring harnesses disintegrate with time and thus affects all the distribution of power in the car ( this causes the backfire noise that usually does not come from the same place ) I once faced this problem and many other C-Class owners too.

Goodluck !

 

Thanks for the replies! After doing extensive research online, I am suspecting the wiring harness. These backfire symptoms started shortly after getting the head gasket replaced. During the head gasket job, the movement of a faulty harness can trigger these issues. I have 6 weeks left on my extended warranty and I'm bringing the car in to be checked... again! This time I am taking the tech for a ride because I don't want to hear that they could not duplicate the backfire.

I will follow up with good news I hope. Being the second owner, I am extremely grateful for my extended warranty. It was the best investment I made because I have had mucho work done at minimal expense. If I can get this harness changed under warranty, I will have knocked out the two weak links of the C280: the head gasket and the wiring harness...among several other items.

More to follow...

 

I finally got the Mercedes dealer to finally stop chasing codes and replace the engine wiring harness. The warranty is covering it completely without inspection. This must have been a common repair in the warranty company's database. Incidentally, the cylinder head gasket replacement triggered all of the crazy engine harness issues. They must bend it and move it around enough so the deteriorated harness starts acting up. When I brought it in this last time, there were codes for 2 or 3 cylinders misfiring, oxygen sensor, airflow sensor, emissions blower unit. I pleaded for them to visually inspect the harness. They replaced it and no codes! They are replacing the spark plugs and boots while in there. Thank goodness for extended warranties and for the internet and these forums to inform us all.

By the way, where can I find a good service manual for this car? My warranty is up in one month!

Thanks,
Quigley