Hello all.
I have a 1989 760 GLE with a B280F engine, LH fuel system. About a year ago the car started having erratic idle problems. I took it to a Volvo mechanic, who throughly cleaned the throttle body and did some troubleshooting. He determined the ECU needed replaced. Prior to that I had purchased a new idle control valve. I had ordered the ECU (refurbished with a 1 year warranty, for $325.00)and decided while I was waiting for the ECU, I would again clean the throttle body. I cleaned everything without taking the throttle body off the car, I did not mess with the TPS. I put everything together, and the car would hardly start and when it did, if you put it in gear at any rpm, it stalled hard.
So I installed the new idle control valve and the idle hunts between 1000 and 2000 rpm. At this point I unplugged the TPS wiring harness and the car jumped to 3000 rpm idle and stayed there, not even a skip. I shut the car off, reattached the TPS wiring, but took off the idle control valve wiring harness. The idle hunts between 1000 and 2000 again, but now it can be driven without stalling. The car is currently sitting in my driveway awaiting the ECU. Any thoughts on this situation? I had read just about everything on these forums on TPS, ECU, Fuel system type problems, but am still unsure why the car would not run after I had cleaned the Throttle body myself. The new ECU should be here within days.