I have the same problem with my 2000 Ranger. When I unplug the IAC it will die. when I plug it back in it will rev high. Sometimes I can bring the idle down when coming to a stop by not clutching until it almost dies and the idle will be fine until I depress the gas pedal again. I thought it might be wiring because moving the wiring harness around would make it stop sometimes. But now I can't get the idle to slow. Another thing I noticed is the air conditioner will not cool when I am having this problem.
The ecm will tell the iac to idle up when it senses the ac is turned on.If the ac compressor doesn`t come on,there is no resistance on the motor,but the motor does not know that,so it idles up.Find out why the ac is doing this,it wouldn`t be low on freon,it would have to be,most likely the ac clutc going bad.Try this,turn ac on and when ac clutch goes off,be ready,and don`t get hurt,tap it lightly with a tool or something,but be carefull!.If it clicks back on,try it again when it stops,to make sure.This will tell you the ac clutch/coil assembley is bad.
You can clear that code light with a hand held scan tool at the auto zone.And they will most likely tell you the code,most likely iac (sense you unplugged it while it was running).This would be a false code,pay it no mind.They will tell you if there are any more codes stored.Of course there is the probability the iac is still bad.Check the air cleaner,and the mass air flow sensor,for trash,or restriction in the air tunnel leading to the intake.Also pick up a can of intake spray cleaner and clean the plenum (upper intake).This will do it a lot of good,even if it does not help the problem.Check for a crack in a vacuum line some where,look hard,they are hard to find.Check the plug in to the iac,it could be to loose to keep contact.If the ac is off do you still have this problem?If not we can rule out the problem I mentioned with ac clutch earlier in my other post.After the codes are cleared,and you have done all the other things I mentioned,drive the truck for a while to see if another code may set.If the code for the iac,comes back on,then you might say that the iac is bad.but i would use a sip tie and tie the plug tight to the iac if you can to see if that fixes the problem.Let me know something back if you would,I hope this helps.
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SOURCE: 1994 Ford Ranger, turned into parking lot and
look under your dash driverside at your clutch pedal and there should be an arm that goes through the firewall and to your pedal if it is disconected reconect it if not then check your clutch fluid
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yes the check engine light is on, it came on when I was trying to get the idle to stop by unplugging the iac but it has been on ever since.
Is the check engine light ever on? There is an A/C cutout relay for when the rpm and load are under high demand, but I don't think this is enough to actvate it. Does the throttle body have a lot of carbon buildup in it? This will hold the throttle plate open and make the IAC pintle stick in it's bore. The IAC will still release with it's return spring when you unplug it, causing the engine to die(no air). I have seen this before, but don't remember one with the A/C cutting out.
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