a different iac problem?

I have two 96 xj's. I just bought a one for a DD. The check engine light was on when i bought it. Code 25 (p505) IAC. Sounds easy right, but NO. First i tried swaping sensors, and throttle bodies, then i replaced the IAC, and TPS. still throws the code 25. cleared the code with a scanner, and the code will turn off, until i put the key in the ignition again.
(this points to wiring) I also simulated it using a bad IAC with my other 96 xj aswell, and there WAS a differance. In the dd, the code is there from the moment the battery is connected, on the trail rig it only comes on after it has been started.
so i figure it is the wiring/connector. But i do get voltage or restance through all wires, i have even swaped computers with no difference.
another thing. i can tell that the computer is opening the iac, i can manually close it, start it and it will open up, but it wont close by it self.
no fix, no smog, no reg., no DD

im going nuts with this. Hope to get some input.

I had a similar problem, ended up there was a short causing the code. Turns out the short fried the ecm, fixed the short replaced the ecm and all was kosher.

Problem Fixed... unpluged all sensors and removed all the wire loom back to the harness split at the fire wall. I found a smashed and broken wire at the kink in the harness, as it goes to the plastic harness jacket by the fuel rail. It appears to have been actually pressed on a few wires, at the factory.
The wire short caused the check engine light to come on immediatly and stay on, as opposed to the other xj's check engine light coming on after the vehicle has been started, and realized the the sensor was not working properly.