I installed a rebuilt motor and trans in my 93 960 wagon this weekend. It started right away but has been idling at 1500-2000 rpm ever since. I have tried every diagnostic test in the book and can't get the idle to drop.

I keep getting DTC engine codes 411 & 223, throttle position sensor TPS & idle actuation controller IAC.

I have done the following to no avail:

Swapped TPS with the original motor.
Swapped the IAC with my other 960.
Swappped the ECU to my other 960...ran fine.
Ran the IAC troubleshooting test...could not get proper voltage (6.0-8.5v)on pin 1.
Verified continuity through all the IAC connections to the ECU.
Shot lubricant into the IAC.
Disconnecting the IAC connector while idling has no effect.
Ran the DTC test that verified the ECU saw closed throttle position (CTP) and wide open throttle (WOT) from the TPS.
Ran the DTC test where the IAC is actuated...successful.
Pinching the IAC hose to the intake will cause the idle to drop.

I didn't change any sensors on the rebuilt engine as it was running when I bought it in November 2003.

I don't know what to do next and would appreciate any insight into possible causes.

Thanks.