About month ago, my MY02 ML 320 started to vibrate a little when idling. It cruises perfectly on freeways. It vibration can only be felt from the floor and the steering wheel is rock solid at any time. There is not a single light lit, so I figured my dealer won’t be able to find out anything wrong anyway. I also thought it might just be an engine mount caused by my new commute route involves some real rough roads.

Last week, when I was trying to get into traffic early in the morning, I stepped on gas a little bit more than I like to on a cold engine, about 4K rpm, and suddenly the whole truck vibrates badly and almost lost power, and the CE light is on! I almost felt happy to see the light (weired I know). I gave it a little bit more gas to get the truck going. It smoothed a little, and I got to my dealer which is about half mile away.

The second day, my advisor called me and said misfire in cylinder 1, ignition coil and wire replaced under warranty. I test drove the truck and it seems perfect now. The work order says:
PERFORMED DAS TEST CODES P2050, P2051, P2043, P2044 IN ME, MISFIRE CYLINDER 1, ELECT TEST COIL AND WIRES, BAD, REPLACED #1 COIL AND WIRES

I’ve searched this forum and literally all over the internet and found no one else reported this problem on a W163. How come it happens? Open the hood; I sure can see a brand new ignition module, with the exactly same PN as the rest five. Why could this happen? What could be the reason? Should I worry about the rest five modules to fail?

One thing I thought might remotely explain the cause would be that I had the truck serviced for the first “B” which involves replacing air filter, and the technician might accidentally knocked on the ignition module #1 which is directly under the air filter box. Is it even possible?