Hey all, my 88 Ranger is idling way high. I bought it a few weeks ago. Been though it several time trying to figure this out. when I got it, it was throwing a TPS code, adjusted the TPS to 1.0 volt at idle then cleared the code and reset computer. Idle dropped to 800-900, then a few days passed and light would come back and idle would raise to 1500 or higher. found out the tps had a dead stop. sometimes no volts at rest. changed it out, reset computer now it still idles at about 1700 consistantly. Runs great other than that. I've checked the timing, and checked for vacuum leaks. all looks fine. TPS is set right at 1.000 volts at rest. don't think its the IAC because its a steady idle, not going up and down. when I unplug the IAC it doesn't change the idle at all, thought that was strange. if I unplug the MAP vacuum it wants to die, seems normal. Not throwing any codes that relate to idle. any ideas? I've already clean the IAC with choke cleaner. didn't help. wondering if I shorted it out by doing so. is there anyway to test the IAC with a volt meter like the TPS? thanks for looking. Smitty

 

the iac shouldn't short, but i'd triple check for a vacuum leak when those small hoses get old they can break really easy

 

Thanks for the reply Banger. I checked again for a vacuum leak using brake clean and starting fluid. I've check every hose carefully. Thing is, it was running good the first time I reset the computer when it still had the bad TPS on it, it only started running bad when the check engine light came on when the tps threw a code. after replacing the tps, no more codes. It doesnt seem to be surging like its trying to find the idle, but it kinda bounces from 1500 to 1700. tps is set at 1.000 volt and hasn't changed. going to the junk yard tomorrow to pull some IAC's just to see if thats the problem, just don't understand why its idling so high...

 

yeah its got to be a vacuum leak or the IAC, since you don't have a don't have a MAS, it kinda sound like your IAC is stuck open since it didn't change when you unplug it, usually when you unplug it it barely idles