Rising and falling throttle at idle.

[Richard van der Hoff]

John Sherrow wrote:
> I would suspect the ISV not a vacuum leak.
> 
> Engine vacuum is pulling air past the ISV rasing the idle till fuel cutoff
> that's why the idle cycles.
> 
> I suppose you're using the heat also now that fall is here. The climate
> control boosts the idle to compensate for compressor load. You might be able
> to back the idle screw down aways to stop the problem. But likely the ISV is
> shot.

Or just sticky. They always get clogged up with crud and need cleaning
out every couple of years, and are responsible for all manner of uneven
idling problems. Certainly make sure the valve is free to move before
you go hunting vacuum leaks.

HTH

Rich