I'm trying to fix a sickly 2002 Mercedes A160 (petrol) for a friend. It is misfiring badly and the check engine light is on. After some faffing around I eventually managed to get the OBD-II information out and it says "P0301 Cylinder 1 Misfire Detected". Hmmmm, I thought it might be able to offer a bit more info than that.
I changed the plugs, reset the ECU, but still the same.
My question is, can anyone suggest what the likely cause could be, or possible other things to look for?
My first thought is the ignition module. But it operates on pairs of cylinders - could be that but then I would have thought that it would fail on two cylinders?
Next I guess it could be a valve/compression - but getting a compression tester in there looks like it will be very difficult to say the least - the plugs are really awkward to get at.
While the car was under warranty (at least 10K miles ago), due to some kind of gearbox/ECU fault the engine over-revved and bent one or more valves which were replaced by the dealer. I'm hoping that this problem doesn't relate to that.
Any other thoughts/advice gratefully accepted.
TIA