S2 idle speed problems

[MadMax]

My '91 S2 sometimes idles smooth and steady. But most of the time, the idle 'hunts' from ~820-900 rpm and when it dips down to 820 it shudders a little as it seems to recover to normal idle. It stays there for a couple of heart beats and then repeats this scenario. It is even more pronounced with the a/c running. Any advice or ideas?
Regards,



------------------
Max
91 944S2 Cabriolet
89 911 Carrera (fomerly)

[Magnus_944]

I'm not familiar with the S2 but I guess it has an Idle Control Valve that might malfunction and cause this kind of problem. Vacuum leak or bad O2-sensor can also do strange things to your car.

/Magnus