I recently purchased a 6 speed manual 2006 DB9 with a bad throw out bearing. Besides the noise when the clutch was pressed, engine ran beautifully and car was overall excellent. I changed the throw out bearing, flywheel, and clutch myself to save the ridiculous labor costs and went fairly well. However right after finishing the job and almost immediately when the car was started, I got a check engine light and emissions warnings. Plugging in the scanner, I see cylinders 7 and 12 are misfiring. After going for a test drive, the misfires come in and out and there's a notable loss in power when they're misfiring, likely because PCM shuts down those cylinders.

A few notes:
- to pull the torque tube to change the clutch, I had to loosen the engine mounts to tilt the engine rearward, which may have pinched something between engine and firewall
- I used OEM flywheel, clutch, and throw out bearing from Scuderia parts, although the clutch was slightly different than the one in vehicle it is the same weight
- the misfires in cylinders 7 and 12 happen together, I've never seen one misfire without the other (codes P0300, P0307, P0312)
- misfires will be present for a few minutes, then go away, then come back all while driving
- because the 2 cylinders misfire exclusively together, I don't believe it's injectors or coils
- coils were replaced in September 2023 under previous ownership and 500 miles ago

I'm stuck here after spending hours poking around. Any input or things to check is greatly appreciated.
Thanks!

 

Did you unplug the battery?
If so, you might have to do the misfire learning procedure.

 

No, I never unplugged the battery even during the clutch change.

 

Could be ?https://aston1936.com/2016/03/18/rel...on-martin-db9/
Also, there is a 70 to 30MPH coast down procedure outlined in the DYI section of this forum. Manual shift is mentioned
Good luck with it!

 

Thanks for the link, I've only ever seen that for battery disconnect and never saw the relearn associated with the flywheel. Nothing specific mentioned in there about changing the flywheel, but since it mentions learning flywheel profile I'm assuming a new one will require it. I will try that tomorrow night when the rain stops.

 

just a note that it’s 70-to-40 MPH, not 30. I reviewed the service bulletin and performed the procedure earlier today, so I’m quite sure of these numbers.

 

I figured it out - it was the misfire learning procedure, BUT I had to unplug the battery to wipe out the old records. It seems once the PCM learns the flywheel profile that it won't relearn a new one by running the drive cycle, so it had to be forgotten first.

Thanks for the replies.