Shawnliew88

Hi all,

I have a 1990 s4 and normally when the car is running at warm temperature, and I come to a complete stop while in gear D at the lights, I get rough idling, any help would be appreciated on how to identify this problem.
Thanks

Shawn

Mongo

Hi, when was the last time the oxygen sensor was replaced?

Rough idle could be many variables. On cars that have not had the intake manifold pulled for service, the idle control valve (ICV) is a likely culprit. Other sensors that could cause an erratic idle are the Temp-II sensor and a failing MAF.

A shot of WD40 in the vacuum line tee-ing to the brake booster and down into the throttle body will tell you if the ISV / ICV (whatever you choose to call it) is failing as soon as the idle smooths out.

Good luck!

Shawnliew88

Thanks I will get it checked out !