I’ve been dealing with misfire issues for sometime now with my 07 S6.
- Last month, had misfires higher RPM and axle vibration. Replaced the axle and took the car out for a run. Full power, ran strong. Fast forward a week, CEL came on for misfire during some throttle @4k RPM - Got worse and could not go quarter throttle at highway speed without a flashing CEL.
Found a couple cracks in the oil separator hose (long over intake plenum) wrapped cracks, seems OK but will need to order a new replacement to make sure - $200 plastic part.
- Pulled codes - cyl 2,6,7,8 all misfire CEL at 4-5k RPM - car was idling OK, and could be driven lightly. Got worse as engine ambient temp increased - could be the oil separator wrap loosening up with heat.
Replaced 2,6,7,8 plugs and swapped coil packs. Plug tubes had oil up to mid of plug. Can’t tell if valve cover or lower. Re wrapped oil separator hose (seems sealed - can’t hear or feel air) and now car won’t idle without flashing CEL - very rough. Pulled codes and 2,3 both misfire at 700-800 idle speed.
I’ve checked all vac lines I can find (cannot reach line under IM) and don’t see any splits.
Pulled, swapped and tried different plugs and coils on 2,3.
Unless the oil separator hose is leaking vacuum that I can’t feel/hear, along with the higher RPM misfires mentioned above, it must be Injector related; weak higher RPM, maybe leaky at idle.? Car had a carbon cleaning a year ago.
Thoughts would be appreciated. I’m most likely bound to order 5 injectors Monday, luckily at cost ($70 each) for 2,3,6,7,8 and see - since no other cyls were suspect yet via vagcom.
Thanks guys!