High idle after IAC replacement

Hey guys, my jeep was having trouble idling and generally running kinda crappy so on a whim I decided to clean my IAC, which in turn made it so the Jeep wouldn't idle at all. Assuming that I was a little rough cleaning it and that I must have broken the original IAC I bought a replacement from NAPA and installed it, and now the Jeep starts fine and stays running but idles at close to 3k. I replaced the throttle body gasket and couldn't see any disconnected vacuum hoses, so any suggestions are greatly appreciated. Almost forgot, it's a 1998 4.0 with 206k on it.

The computer might think the pintle is still set relative to the old unit. Did it come with instructions? Sometimes they say to fully eject the pintle. You could also try clearing the computer memory. Check for vacuum leaks and physical binding problems too

Testing the TPS and IAT sensor per the FSM might also be revealing.

There also should be a rubber o-ring that goes between the IAC and the TB.

I chased a high idle for months until I sprayed the TB with carb cleaner. I put an o-ring on the IAC and it solved the problem.

Ok so it's definitely the IAC that's causing my high idle. Someone mentioned that the pintle might need to be extended, and this made sense since it seemed a lot shorter than the one I removed since it was compressed and it was allowing too much air in causing the high idle. However I extended the pintle and now it's back to not being able to idle at all unless I give it some gas. The IAC came with no instructions at all, so can someone tell me what I'm doing wrong?

I would also check the TPS. It should be reading less than 900 millivolts (.9 volts)at idle and should gradually increase to no more than 4.5 at WOT. The orange/blue wire is the sensor output.

The IAC may not be getting a power/ operating signal. May be a wiring harness or connector problem. I installed a spare IAC in my throttle body, and then connected the wiring harness to the new IAC, while the new IAC was loose, then cycled the power on and off, to see if the pintle moved. I was careful to make sure I did NOT let the pintle move very far, before disconnecting the wire harness from the IAC!!!!!!

If the installed IAC pentle is too short, and the idle is high, then temp connect the harness connector to the new IAC for 2-3 seconds, to see if the new pintle extends out. This way you visually verify the entire system, ECU, wiring and IAC.

XJcory said:

Ok so it's definitely the IAC that's causing my high idle. Someone mentioned that the pintle might need to be extended, and this made sense since it seemed a lot shorter than the one I removed since it was compressed and it was allowing too much air in causing the high idle. However I extended the pintle and now it's back to not being able to idle at all unless I give it some gas. The IAC came with no instructions at all, so can someone tell me what I'm doing wrong?

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Did you check and see if there's a vacuum leak around the seating surface?

I don't think there's a leak around the seating surface. At idle I can hear the air being sucked through the iac port and if I hold my hand over it I can slow it down and even stall it so that seems to be the problem.