Volvo: 1993 Volvo 940 Turbo idling problems, vacuum leaks, 1993 volvo 940

Question
Dear Ray,
My 1993 Volvo 940 Turbo has an idling problem that I couldn't get a straight answer for yet. When I start the car, the engine idles 1500rpm (not good) but after about a few minutes of idling this high, the engine calms down to 1000rpms, then stays unsteady at 1000. After that, the rpm would jump down to 500rpm, then go back up to 750rpm and be uneven at 750. I checked the throttle body and the IAC sensor. Neither are overly dirty, but the IAC does measure 8.5 ohms of resistance. What could my problem be? Where do I need to start looking?

Answer
Yochwa,
Check for vacuum leaks at all the intake areas. Clean out the throttle hosuing and make sure that you hear the switch "Click" as the housing is opened. Adjust the switch as needed. Read any fault codes that are stored and see where they lead.