Misfires During Acceleration
Thread Starter
Senior Member
Joined: Aug 2014
Posts: 370
Likes: 31
S55 AMG
Misfires During Acceleration
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.
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.
Member
Joined: Nov 2012
Posts: 220
Likes: 2
From: New England
2006 S430 4Matic
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.
Thread Starter
Senior Member
Joined: Aug 2014
Posts: 370
Likes: 31
S55 AMG
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.
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