Steven C.

My 89 S4 automatic will all of the sudden raise the idle about 300 rpm for no reason at all and then go back down again? Does not happen very often but it will surprise you as the car leaps forward and you apply more brake to stop it. At the same time it has become harder to start cold first thing in the morning.

Any suggestions on where to start looking are appreciated.

Steve Cole
89 928S4
90 911C2
71 Vintage Fiat racer

Schocki

ISV going out (most likely).

Mine did not run smooth after the first start attempt when cold. Ran sub-idle for a few seconds and was fine afterwards or stalled. It always started on the second attempt and was just fine all day.

You can try 3 things:
1. Lubricate the ISV (use search function)
2. Disconnect the MAF (don't forget to disconnect the battery) and start the car without the MAF. This forces the LH-ECU into Limp home mode and the ISV is not adjusted by the computer. If the car starts better it's most likely the ISV.
3. Join Rennlist and get in contact with somebody in the Dallas area with a Spanner. They can isolate the problem in no time. They are ALL great guys too