2002 4.6L racing Idle, no upshifting.

[Noslo351]

My wife's X decided to act up today. On the highway it seemed like it wouldn't shift out of 3rd. We got off the Highway and noticed the idle was racing. When she stopped and put it in park it was idling around 2k. I disconnected the IAC valve and it just about stalled, Reconnected and the idle shot back up. Shut down the engine and disconnected the battery. The problem fixed it self. This happened a month ago and the battery trick worked, I cleaned the IAC also thinking it was gummed up.
Any ideas where to start looking for issues?

 

[zerodevil]

My first bet would be the IAC valve, you might also get the computer ALP cleared and upgraded/reflashed at ford. If its self correcting i dont think its a mechanical problem.

 

[Noslo351]

The computer was upgraded to the latest calibration code per TSB 03-14-7 this past spring. The IAC valve may be going but that does not explain the weird no upshift problem when this glitch happens. Its almost like the ECU thinks its full throttle and holds out on shifting. Maybe its a TPS issue?

Any other suggestions?

 

[zerodevil]

well its hard to say, ford has so many safe-gaurds built into the stock PCM programing that it may be putting the truck into the fail-safe mode. Or it could be that it is detecting to much incoming air for the given TP, and is waiting before shifting. After the battery trick the shifting problem disapeared as well?. how old is the battery? and are the terminals in good shape and tightened securly? these trucks do some odd things when the battery isnt hooked up tight and in good shape. If it was me i would replace the IAC and the TPS (its cheap and easy) and then see where i was.

 

[Noslo351]

It's got an Optima that's about 5 months old and the terminals are clean. Yes, the controls righted themselves after pulling the battery, shifting and all. I'm going to clean the MAF before I start throwing parts at it. Between the IAC and TPS that's $120, I don't want to throw away that money if I don't have to.

 

[zerodevil]

Ouch, i thought my IAC was $60ish from NAPA, and i got a BBK tps for around $25. My money is still on the IAC (is it still the factory orig?). because it should have died imediately when you unpluged it, tells me its not closing all the way, which is either due to dirt, or the servo going out.

 

[Noslo351]

Yes the IAC is original. The engine did stall when I pulled it the first time. I momentarly disconnected it a few times after that but pushed it in back just before stalling.