Unfortunately my issue has not been resolved yet.

I just tried replacing all coils with new, no change.

As a workaround for now, I used ByteTuner to change c_mis_max_nr_off_iv to 0 in the DME tune. This value controls how many cylinders are shut down when a misfire is detected. Default value is 2. I changed it to 0. I don't have cats, so no need to shut down cylinders if there's a misfire. Now when it does occur I get a single brief flash of the SES light, but otherwise I can't tell anything is going wrong, the car drives so good.

Updated list of things I've tried:
  • Replaced all 6 spark plugs with new
  • Replaced all 6 coils with new
  • Replaced cyl 6 fuel injector and inspected the electrical connector
  • Confirmed AFR of about 11:1 at the time of the misfire (suggesting the fuel system is keeping up fine since its not leaning out)
  • Removed the ESS manifold and pressure tested to ensure the intercooler wasn't leaking coolant into the cylinder, pressure tested good, held 11psi for over 4 hours. Resealed manifold to head, fresh gaskets, torqued to spec.
  • Compression tested: between 209 and 211 psi across all 6 cylinders (gauge is out of calibration, its probably 20-30 psi off)
  • Free-rev to 6k RPM, held there, no misfires. Also drove in 2nd gear and held RPMs at 6300 for a few seconds, no misfires. It only happens under sustained load such as in 3rd+ gear wide open throttle.
  • Installed M3 motor mounts to match M3 trans mounts
  • Flashed known good tune used on prior track days to the car, still misfires
  • Replaced headers and installed all new hardware and gaskets, confirmed no exhaust leaks


I'm starting to doubt some of my tests at this point, such as the pressure test I did on the ESS manifold. I applied 11psi to the inside of the intercooler circuit, which is the opposite direction of the pressure applied when the car is under full throttle. I should have applied vacuum to that circuit to better replicate the real world.

I guess the only other thing I could validate is the wiring harnesses. Ignition looks solid, and it routes in a place that wouldn't be effected by the clutch job, and its right on top, and everything looks super clean with no cracks in the sheathing etc. But the fueling wiring harness is harder to inspect due to it routing behind and below the huge ESS manifold.

Deathtrap, its interesting you repaired your ECT wiring, I wonder if an intermittent bad reading there would show up in some logs.

I'm going to run a fresh log on the car to validate fueling stays strong, which I believe it does, but can prove it now that the DME isn't shutting down cylinders when a misfire is detected. I'll log ECT too and see what that looks like.

It seems like these are the remaining possibilities at this point, probably in order of likelihood:
  • Intercooler coolant leak
  • Fueling wiring harness fault
  • Cam sensor failing intermittently? (seems highly unlikely or the symptoms would be different?)
  • Harmonics issue with the ATI damper, Sachs performance clutch, and OEM-style LUK dual mass flywheel (also seems highly unlikely)


I cant think of anything else that it could possibly be, anyone else have any thoughts on this?