Misfire Cyl 7 under load/WOT - Plugs, coils, injectors already replaced

[paul_80eighty]

Hey guys, I've owned my F13 M6 for around 8 months now and love it. However I've run into an issue that started about a month ago.

When in 2nd gear or higher, I noticed a stutter/hesitation when doing a pull. This problem started gradually. The first time it happened I wasn't even sure if I fully noticed it. The next time, it threw drivetrain malfunction at me. This would happen at 75% throttle or more.

For context, I've got aftermarket charge air coolers, Charles's DPs, fatback exhaust and an ECU tune.

So, I changed out my plugs to NGK 97506 1-step colder gapped to 0.024. This did not fix the issue, although it was time for a plug change anyway. Then, I changed out ignition coils. This did not fix the issue either. Finally, I changed out the injectors in bank 2 (since the misfire is cyl 7). I really thought this would fix it, however it did not. I did notice a slight improvement - I had to drive a bit harder for it to throw the code again. But regardless, the issue persists. The only code being thrown is cyl 7 misfire.

I've tried reverting to stock tune without success. But in doing this, I noticed it took driving the car a bit harder as well to get it to throw the code - which makes me think it's still a fuel system issue.

Idle is smooth, and driving the car normally I don't notice anything wrong whatsoever. It could be so many things, but wanted to see if anyone has had this issue before where there's a persistent in one cylinder only under load heavier load (1st gear pulls still rip to redline with no noticeable issues). I haven't noticed any unusual smoke from the exhaust or any unusual smells either.

Thank you for any input!

[M5Rick]

Originally Posted by paul_80eighty

Hey guys, I've owned my F13 M6 for around 8 months now and love it. However I've run into an issue that started about a month ago.

When in 2nd gear or higher, I noticed a stutter/hesitation when doing a pull. This problem started gradually. The first time it happened I wasn't even sure if I fully noticed it. The next time, it threw drivetrain malfunction at me. This would happen at 75% throttle or more.

For context, I've got aftermarket charge air coolers, Charles's DPs, fatback exhaust and an ECU tune.

So, I changed out my plugs to NGK 97506 1-step colder gapped to 0.024. This did not fix the issue, although it was time for a plug change anyway. Then, I changed out ignition coils. This did not fix the issue either. Finally, I changed out the injectors in bank 2 (since the misfire is cyl 7). I really thought this would fix it, however it did not. I did notice a slight improvement - I had to drive a bit harder for it to throw the code again. But regardless, the issue persists. The only code being thrown is cyl 7 misfire.

I've tried reverting to stock tune without success. But in doing this, I noticed it took driving the car a bit harder as well to get it to throw the code - which makes me think it's still a fuel system issue.

Idle is smooth, and driving the car normally I don't notice anything wrong whatsoever. It could be so many things, but wanted to see if anyone has had this issue before where there's a persistent in one cylinder only under load heavier load (1st gear pulls still rip to redline with no noticeable issues). I haven't noticed any unusual smoke from the exhaust or any unusual smells either.

Thank you for any input!

I'm no real tech but when it happened to some of the others they changed out the usual like plugs, coils and injectors like you did then found the HPFP to be the rogue especially in tuned motors, try cleaning the MAF's also.

[M5_Raz]

What Rick said. But it could be a lot of things, at this point I would take it in to a good shop before you damage the engine