Every morning especially, when its cold, after the engine warms up about half way, my h23 starts revving up and down between 1k-1500rpm. This difference becomes samller and smaller (then 1200-1400... smaller). Also after a 90 mile trip, after I got off the highway, at idle it started doing it again. What could be the problem. Also, after I drive the car for a little bit in the mornings (.5-1 mile) the problem goes away. Also, the engine idles rather high a lot of around 900-1100 rpm. Other time its fine.

 

IACV could be dirty. there are 2 bolts that hold it on to the backside of your intake manifold. I think there 12mm. take it off and use some brake cleaner to clean the 2 screens just sometimes they can be carbon buildup.

Also on the side of the IAVC there is a plate with 2 screws that open up to a white looking thing (hard to describe) what you have to do is turn it so that you don't have a irratic idle when it's cold.

I'll try to get some pics for you man

 

What is the IACV?

Thanks