My astro runs well and I service it on a regular basis, but lately it has been idling too high. I changed the AIC and the O2 sensor but no improvement. I also checked for and repaired vacuum leaks, still no improvement. Sometimes it is slightly better when its warm. Any suggestions :banghead:

I am experiencing the same issue with my 86 astro. I have replaced the AIC, the O2, the MAP, the TPS, and as a last resort -- the computer.
The only piece of the puzzle which seems to allow it to idle down what-so-ever is the "TPS" or Throttle position sensor, located in the center of the throttle body, passanger side, above the manifold. When removed, the engine idles down to where it should be, when in place the engine idles up. The only minor adjustment that seems to be able to be made to the TPS is to loosen it up and tilt it one way or the other (angle it slightly) but it just doesn't cut it for me. You may want to look into it though as every situation is different.

After reading many other make and model forums I tried what many were suggesting. I removed the throttle body and there was the problem. The gasket was missing a big piece and the PCV inlet was plugged solid. I cleaned the throttle body up and put it back on with a new $4 gasket and it started up and runs perfect. This forum saved me hundreds of dollars in shop repairs and now my "88" astro runs like new.

After having the same problem with high idle and searching this forum, I did excactly what is stated below and found the EXCACT SAME CONDITIONS. After replacing the TBI gasket and PCV and cleaning out the vacumm port for the PCV, my Astro now runs and idles like new!
The gasket becomes brittle and breaks up and gets sucked upward into the vacumm cavities of the TBI, wrecking the idle and PVC operations!

After reading many other make and model forums I tried what many were suggesting. I removed the throttle body and there was the problem. The gasket was missing a big piece and the PCV inlet was plugged solid. I cleaned the throttle body up and put it back on with a new $4 gasket and it started up and runs perfect. This forum saved me hundreds of dollars in shop repairs and now my "88" astro runs like new.

Blown out TBI gaskets were very very common in the late 80's and 90's. And will always cause a high idle, as the intake air bypasses the IAC, which is basically a regulated vacuum leak. Easy to diagnos, just spray some brake clean or carb cleaner around the base of the TBI unit and listen for any change in RPM.