Hi my 88 has the dreaded fast idle ,between 2500 and 3k ,but not all the time I have changed the iac and have started to check all the grounds.it will drop down the rpms after a about 20 min. Of running ,but who wants to wait that long ! It seems like the computer is slow ,or that it may be getting inputs to idle that high. One other thing sometimes when I set the cruse control it sometimes takes a really long time to set . Any thoughts

 

Sounds like a typical tps problem, its either bad, or out of adjustment. vacuum leaks can also give you a high idle, but are usually more consistent. If your throttle body is dirty, your aic might be sticking too.

When ever I have a high idle problem I yank the throttle body and douche it out(remove the tps, they don't like cleaners!!) and then reinstall the tps to spec.

Simple tps adjustment/install guide:
http://autorepair.about.com/library/faqs/bl232i.htm

 

Yea I think I'm doing to put that on my list to check,this thing is weird its like when I turn the key on and before it starts ,its like the iac gose wide open!

 

mine has this problem too. it is the TPS 100%. if it is not constant and only sometimes