Once you leave the battery disconnected for at least 5 minutes you have to drive it up to maybe 50 miles or so for the PCM to relearn the system. You have a few days between now and Tuesday try it and see. It might even be more miles for it to learn.

 

Will do. As you say I'm not getting a new IAC till Tues anyway. Thanks 1more. Appreciate your help.

 

HHhmmm...... Try this trick before buying a new one....

Disconnect battery.
Turn on headlights.
Wait 3 minutes.
Turn off headlights.
Reconnect battery.
Turn ignition On, (but not to start)
Count to ten.
Start engine.

See what it does. When you reset the PCM, it needs to relearn the 'zero' values for all the various sensors. Need to give it time to do that.

 

Tried it. No difference. I also tried another thing I saw on U Tube. Fire up stone cold engine and pull connector from IAC. Remove IAC and measure how far out the pentile is. Repeat but wait till engine warms up and measure again. Both measurements were identical. Tells me the pentile is stuck, not moving, kaput.

Here is my plan going forward (unless someone has a better idea). I can't buy a new IAC till Tuesday when the dealers open up again. So I'll drive it the next two days. If the problem does not fix itself by then I will buy a new Mopar IAC. I'll put it in and if it fixes the problem then I will live the rest of my life in happiness. If it does not fix the problem then I am forced to have the dealer get to the bottom of it. Might turn out it is not the IAC and I will have spent money on a new part I did not need. But my truck is 24 years old so I don't mind as much buying parts before they die. I figure they are in the twilight of their life anyway and will be one less part I have to worry about.

Thanks all for your help. I appreciate it.

 

Easy test: With ignition On, engine off, unplug the IAC. Check all four wires for voltage. Two of them should have 12 volts. If they do, the IAC is the bad part, if they don't, either wiring, or bad PCM.

 

I'll try that too. A good check to be sure the harness didn't get messed up during the process. Thanks HY.

 

Checked for voltage on the IAC plug. Two contacts with no voltage (or a trace) and other two with 12 volts each. Has to be the IAC. I was very careful when I cleaned the IAC not to twist, turn, push, pull on it. But when you remove and insert it into the throttle body who knows. You wouldn't think simply cleaning the thing would damage it. Maybe I got some brake cleaner in the thing. Like I say, who knows!

 

Yep, sounds like a bad IAC.

 

I'm actually rooting for a bad IAC now. I hate rabbit holes.

When things go bad I like to see smoke and springs shooting out all over the place so I know it is broke and what it is that broke...if you know what I mean.

 

Before you condem the IAC, check for a vacuum leak, especially around the base. Did you reuse gaskets? A vacuum leak will cause a high idle, and in effect let additional air in. If the IAC is closed and you have a leak well.......