My '84 380 SL stalls when it has been run a while and I come to a stop. The car generally idles at 500 rpm when the car is in gear and the engine is good and warm. This seems low to me. I think I may have a bad idle speed control unit but am hesitant to go out and buy one until I am confident that is the source of the problem. The car runs very strong otherwise. Any tips or suggestions out there would be greatly appreciated.