My idle in a 87 740 non turbo won't go below 3000 RPM unless I disconnect the idle control motor and plug the hose. If I do this the idle is 550 RPM. For some reason the computer is sending a signal to the idle control valve to open fully and stay wide open. When this happens the idle goes to 3000 RPM and won't slow down. If I manually close the and then restart the car the valve immediately opens fully and stays open.

I have check the following and the problem still exists any ideas?

Replaced radio surpression relay
Replaced idle control motor with a good used one
Checked throttle switch
Checked throttle plate
Checked for air and vacume leaks, none found
Changed AMM with good used one
Changed engine temp sensor for computer
Checked injector pulses

I'm wondering now if there is a problem with the wiring harness. I had to fix some injector wires with bad insulation a while back. The other wires look ok but I don't know what else would cause this strange problem.