The Jeep: 1997 TJ Sport 4.0 66k miles. I've changed plugs, distributor cap, rotor, and wires within the last 5k miles. Was running great until yesterday...
Yesterday, out of the blue, the idle started to creep higher and was erratic. Now idling around 1200 RPM. I also noticed that the usual idle kick down when stopping didn't happen at all. Up until yesterday, the car idled at around 800 RPM always. The car didn't throw a code.
I looked at the threads on this site and figured that my problem, after checking for vacuum leaks and not finding any, was the IAC. I removed it today and it was pretty crudded up and I also noticed that the threaded nylon sleeve for the pintle was loose and the threads looked bad. So rather than just cleaning it, I decided to go ahead and replace the whole unit. I also removed the TB and cleaned it up really well at the same time.
Well after almost a whole day wrenching, the problem hasn't gone away. The car still idles around 1150 - 1200 RPM. I pulled the connector for the IAC and got a code then. I cleared the code with my scanner and also tried disconnecting the battery to set the engine controller back to baseline - problem still there. I also noticed that the usual "kick down" in idle when the car rolls to a stop still doesn't occur anymore. I checked the speed sensor with my scanner (real time, while driving) and it appears to be operating just fine.
I'm pretty much stumped now and looking for suggestions. Could it be a bad MAF or TPS? Any suggestions would be greatly appreciated. I don't want to start throwing parts at a problem if I don't have to.