
Originally Posted by
duncanm
Idle Air Control Valve.
Honestly -- idling problems that cycle in and out make me think of very few suspects:
1. Aircon is on and there's a problem with the high-idle setting when the compressor is turned on.
if you don't have the aircon on when the problem occurs...
2. Idle Air Control Valve has some issue.
or.
3. There's an intermittent vacuum leak. This sounds less plausible, but you never know. The fuel vapour purge valve cycles on and off. Is there a leak on the non-manifold side of that valve? Try plugging it at the manifold and see if the problem goes away.
btw - I'm not sure or not if you are misusing the term 'limp mode'. Limp mode is when the boost is limited to wastegate pressure - approx. 6-7psi. It doesn't affect idle.