89 s10 2.5 sky high idle?? please help

I have a 89 s10 with 2.5l m/t tbi and its idle is running as if accelerator is on the floor. i have replaced throttle position sensor and now have replaced idle control valve both advised by the local parts store as a sure fix. Now I still have the problem but my wallet is lighter. now i need some good advice. please help:banghead:

I know this may seem dumb but do the throttle plates close all the way? It won't take much of a gap to cause the engine to rev. My father-in-law's blazer had so much crap around the throttle plates when I did a tune up that the peddle would stick.

I know this may seem dumb but do the throttle plates close all the way? It won't take much of a gap to cause the engine to rev. My father-in-law's blazer had so much crap around the throttle plates when I did a tune up that the peddle would stick.

i didn't even think to check that. i appreciate it, i will check tomorrow a.m. and let you know if that cured it. thank you:grinyes:

well i checked the plate and it is closed tight. i was messing around with the iac valve again and i did get it to improve some by lengthening the plunger a bit. I wonder if I am on the right path or creating another problem. I appreciate the help.

Check rubber lines for a vacuum leak. The PCV line going to the valve cover is big enough that if it's cracked, it'll really rev that motor.

The vacuum leak is a very good point, no question it could cause the high idle.

My '86 Cutlass with that motor does the same thing...Pontiac Iron Duke.