Wife's 01 Cavalier has a hiccup at idle that just started coming on. It will idle great, then every 30 seconds or so it will 'hiccup' and drop to about 600 RPM, then come right back up and purr like a kitten again. 142K on the clock, I've done all the maintenance and the car is still a strong runner.

I've cleaned the IAC to no avail, but I'm wondering if the the IAC valve is shot since the plastic plunger doesn't move ( I thought it was supposed to).

I also cleaned TB, new fuel filter & plugs. Still does it. There is no CEL by the way.

Anybody have any thoughts?

just a long shot... but coils?

14.82 @ 97 mph

My 98 has done it since brand new in 98 (I purchased it from my mom in 06).