Ok, I've come to some conclusions about my idle problem on the 86 740 Turbo. Being a mechanical engineer, I hooked up the wiring wrong (interchanged throttle switch & idle air control valve connectors) after a major wire harness re-build. I discovered this by running thru the trouble-shooting procedures in the Volvo green manual for the B230FT engine.

After checking everything else by the manual with no problems found, I decided to open up the FI computer and take a look. Damn - burnt out one of the circuits (terminal 10), one leading to the idle motor. I repaired this with a jumper wire, but still no idle control.

Anyway, I think I have also burnt out what looks like a transistor or mosfet in the same circuit of the computer. The transistor/mosfet has the wording "BDX77" on it and also the number "28609" (which could be a date....as the car is an 86 model).

What are my chances of finding a direct replacement component that I can solder into the circuit board? Anybody know what this component is based on the above quoted codes?

Thanks!

Greg