How can you tell if your idle speed control valve is in working condition? When my car is idling, and I unplug the electrical connector, the idle speed doesn't change.

Turn on your headlights, and whatever else you can to put a load on the alternator. A/C if you have it also. Then unplug it. If your idle drops, it's working. 90% of the time, if it stops working, it will cause your idle to surge really bad.