AlexMercedes

Hey guys, I recently encountered another problem with misfiring (of course). Every time I try to perform what would be called "harsh acceleration," the car suddenly misfires at around 3500 RPM during boost. Right afterwards, the check engine light comes on and the car has a different tone, vibrations, etc.

The weird thing is that when I pull over and restart the car, the misfires are gone. The car drives perfect afterwards, it's like nothing happened at all! I troubleshooted what was going on, and here are my results: When you accelerate smoothly, the car runs fine and no misfires. When you accelerate harshly, the car misfires at around 3500 RPM whenever you start to gain boost. I haven't checked the CEL code yet, but I'm assuming it's only 1-3 cylinders that are misfiring because it feels absolutely nothing like half the engine misfiring (that I've experienced before). This is very weird, what is possibly going on this time? Any help/info is much appreciated. Thanks guys.

tusabes

I have read about this exact problem happening on v12 cars but can't seem to locate the thread

Welwynnick

I've had something similar before.
It seems to be endemic with the V12. Do you have a DTC reader?
That's always the first place to start.


Nick

lganski

Check your Crankshaft Position Sensor. (CPS) I had a similar situation, twice, then it failed all together. The CPS has a high failure rate. Very easy to replace on the 430, I don't know on the V12. Do a search on the CPS.

_Ryan

Check the codes. Symptoms near perfectly describe a failing coil pack.

AlexMercedes

I thought if it was the coil pack, it would be misfiring on startup? I can't check the codes until tomorrow, but I'm assuming it should be from the driver side coils because I already replaced the passenger side coil pack.

G.AMG

This thread is nothing without codes.

Welwynnick

Not necessarily. They CAN cause starting problems, but the usual symptom on any car is misfiring under load, as this is where the greatest voltage demand is.


Nick