I have 2001 Audi A6 4.2 .This is what happened we went out car was running beautiful on way 5 miles from home car started not running right like a cylinder wasn't firing. shaking while idling. no check engine light . Changed spark plugs with NGK Platinum 4s. Coils look good no oil in tubes. no cracks nothing. Not sure about driving it now don't wanna risk screwing up sport cats. Can anyone give me some feedback on this its baffling cause no CEL. I changed fuel pump,filter & starter recently. Everything is new up to thermostat. water pump,timing belt.pullies everything. If this problem is something major why isn't CEL coming on? Passed emissions inspection mth ago. I hooked up my Audi VGate VS 450 scanner and showing no codes. Does anyone know if this scanner shows pending codes?
Thank You