Gavin Lewis

I have a 2007 S6, it runs fine, no issues, but AFTER heavy acceleration the CEL starts to flash indicating random misfires. Thing is last time I checked, the misfires were only happening on Bank 2. I replaced all the coils, and was ready to do injectors, but the fact that the misses are all on bank 2 / ECU 2 concerns me that it may not be injectors. Aside from this issue, the car runs amazing and pulls hard as ever under acceleration. Anyone have any thoughts on moving forward? I was trying to see if I could swap the 2 ECU's and see if the misses move to the other bank, but I can't find anything that says this is possible, and it's more money than I'm willing to destroy in an experiment. Any insight would be greatly appreciated.

raj99

You mentioned replacing the coil packs, did you replace the plugs as well, if so which ones did you put in? Since these cars are very particular relating to gaps and I've found the NGK do quite well.

Gavin Lewis

I did replace plugs with properly gapped NGK-R plugs.

raj99

When's the last time you changed the fuel filter? Are you sure you're getting proper fuel pressure during acceleration?

Gavin Lewis

I haven't tested fuel pressure, so that could be a path forward. I'll take a look, but really with the separate HPFPs it shouldn't have too many fueling problems should it?

raj99

I'd start with the fuel filter...if you've never changed it, that's an easy fix. I've seen quite a few threads of HPFP failures or degradation, which will cause issues exactly like you've described.