W203 / 217 Intermittent misfire
 

Hi,

I have a 2003 W203, C200K, it was running fine until a few weeks ago. It started suddenly to misfire, when I stop, and while the car is idling. Especially in peak traffic. At first it was once in a while, but yesterday evening when I was driving it happened about every time I stop.

I took the car to a mechanic a week ago, as I knew it was due for a service, but even after the service, the misfire continues. He has done the following on the car:
He identified from the computer that the misfire is on piston 2. (After and during the tests he did as below, it stayed on piston 2.)
he changed the spark plugs - and swapped it around
He swapped the coils around,
he cleaned the injectors, and swapped it around
He cleaned the lifters and swapped it around
He swapped coil cables

After all of this, the car still misfires.

I got the car back on Monday, and Tuesday it was driving fine. Yesterday was another story. This morning it have not misfired once while driving to the station (5 Km)

Can it be the computer that is misbehaving, but if so, why intermittent. I can also mention that the car does not overheat, it sometimes happens a few minutes after it was started in the morning.

Can it be the MAF sensor? I saw on another thread that the MF sensor can cause misfiring? I do not want to spent unnecessary money, just to find that the problem is still not solved.

I would really appreciate any suggestions to fix this.

Regards

Using DAS or equivalent, you should look at the smooth running values and report. Also, check and report the short and long mixture adaptations. Throwing parts at it does not guarantee a repair. If you cant access DAS you can should look at the short term and long term fuel trims using a simple OBD2 interface. you can check mode 6 for individual misfire counters.

Swapping bad parts to a new location is not a repair. The point is to see if the trouble moves.