The idle is high, 1500. If I touch the gas even slightly it jumps up to 3000 for 10-15 seconds and goes back down. Anytime I'm slowing down or stop and push in the clutch it'll jump to 3000 as well.

Turning the AC off and the idle goes to 2500, and as high as 4000 if I give it any gas.

I had already cleaned the throttle body, and not having any luck finding a leak. Is the AC providing a clue here I'm missing?

 

IAC Valve is what sets the idle
After engine is warmed up and idling, unplug IAC Valves 2 wires, RPMs should drop to 500 or engine may even stall, either is good it means no vacuum leaks

Also check throttle cable to make sure its not binding, engine off, make sure throttle "snaps" closed, then do the same engine running, try to manually close throttle more, could be bad spring on throttle shaft
There is 18-21" of vacuum trying to suck and hold throttle plate open, so spring needs to be tight and a working

 

Thanks for the reply. Throttle cable seems good, but unfortunately unplugging the IAC Valve wire didn't make any change in the idle. I'm not having any luck finding a leak,

 

With engine idling and IAC Valve unplugged..........................
Pull off any vacuum hoses one at a time and plug that port with you finger, including power brake and PCV hoses

 

Pretty much ruled out a vacuum leak. Replaced the IAC valve and TPS sensor. Replacing the IAC halved the RPM while parked and cleared my CEL, but accelerating still causes the engine to rev to 3.5 rpm and stay there for a bit. If I'm driving, it'll just say there and essentially drive itself.

 

Have been reading non-Motorcraft IAC Valves help but often don't work as well as Motorcraft

TPS doesn't set idle, nothing to do with idle unless it is causing throttle plate to stick open, just FYI
TPS is there to give the computer a "heads up" that driver wants to speed up or slow down so it can adjust spark and fuel for instant response

Only way to raise RPMs on an engine is by giving it more air, if you just give it more fuel you get a flooded engine

So either IAC Valve is not closing all the way, unplug it and see,
or throttle plate is not closing all the way, manually try to close it more when RPMs are high ,
or you have an air leak
These are really the only 3 options

The Computer's only control for RPMs is the IAC Valve, if it gives it more fuel engine will flood and stall

You have a 2.3l Duratec engine and there are more than a few complaints about throttle sticking, didn't see one solution, seems each is a little different

 

So I unhooked the new IAC valve and, like you said up above, the engine settled down to a rough idle. It didn't do this with the Motocraft IAC valve. Compared the two and saw the Motocraft wasn't shut completely. Got a pick and pried it open and inside was a lot of black rubber foam. Got it cleaned out and reinstalled it and while the idle isn't as low as the new IAC (800ish), it's now at 1200 BUT is now responsive to the throttle. No more self driving truck. I may need to take it off and see if I can get it any cleaner, to get the idle down more but the main issue is resolved.

Thanks a ton for the help, I would never have considered the new part being defective. Thankfully I'm just out $20.

After cleaning it some more, idling back at 750. I think that foam must've been in there for over a year now, my idle hasn't been that low in a long time. Guess enough just got wedged in the IAC to keep it open and I guess after enough vacuum builds up it pulls it closed. I think at one point while changing my air filter some of the foam that covers the AC hose fell in.