537playing

With nice January weather today I changed my oil.
After the new oil went in I did not replace the dipstick filler tube tab when I started the engine to recheck the levels.
The engine did not idle smooth. It stumbled and almost stalled.
I replaced the filler tube tab and the engine ran fine again.
In my other (non Audi) cars this wouldn't occur. Why does it happen on this engine?
A6 2.0T

newmoon

I think it messes up the airflow in the Positive Crankcase Ventilation system and allows extra unmetered air into the intake, causing the mixture to run lean and idle rough. The PCV system in a turbo engine is different from NA, or Audi may have set the desired crankcase pressure differently, so this may be why it behaves differently with the dipstick cap off.

DanfZX14

No kidding huh.....

snagitseven

Can I assume since you removed the filler tube cap, you are using a dipstick to check the oil level? If so, you can leave the dipstick permanently in place in lieu of the cap.