91 Ranger 3.0L High idle

[killerjr]

I have had this truck for about a year now, and it has always idled low for me. Never a problem in warm weather, but when it started to get cold I found myself having to sit in the truck and put slight pressure on the accelerator to keep it running until it warmed up. Today I was changing my thermostat and found that the IAC wire was unplugged. Thinking that I had inadvertantly knocked it loose while I was under the hood, I plugged it back in. After I finished the job I started up the truck and the RPMs immediately kicked up to 3500+! I shut it down and unplugged the IAC wire. When I started it back up again the engine was back to "normal".

Is this a bad IAC, or more likely a vacuum leak causing this. I am sure that having the IAC unplugged is why it doesn't want to stay running in the cold. Haven't checked for codes as there is no Check Engine light showing.

[wintonboy]

Jr,
The IAC is nothing more than a solinoid controlled vacuum leak. The plunger in yours is probably stuck. Take it off, flip it over and slosh some injector cleaner around inside. Clean the plunger shaft with a few Q-tips and make sure it moves smoothly. Also gentilly scrape the orifice clean with a piece of plastic. Bolt it back on and fire up. If you still have problems, Aotozone's web sight has a good repair guide with the specs for the IAC

[wtousand]

I agree, cleaning the IAV sounds like the most likely solution. There is one other possiblity if this doesn't solve it. Since most computers "learn" the best settings after driving for a bit, I wonder if the computer didn't try to set the IAC to full open while trying to correct the low idle condition. If so, when the wire was reconnected it might drive the air valve open too much, resulting in instant high idle. Driving might correct it or it might just drop on its own after the first few starts. One other way to reset the computer would be to disconnect the battery cable for a while. Then the computer should go back to fairly safe default settings until it relearns new normal conditions. Just a thought.

[DonSor]

Shouldn't there be some indication fromt the Cehck Engine Light as the problems described seemed to be PCM related?