using some information from this board, I cleaned the idle control valve on my car by removing it (you have to remove the air cleaner housing on my car, a 1987 300E, to access the valve) and squirting a bunch of carburetor cleaner into it and shaking it repeatedly (cover the ends with your fingers while shaking it). If you can hear valve inside freely moving back and forth when you shake it, you probably don't need to replace it. If it is dirty, it should be moving more freely after you clean it.