Three months ago I bought a 2002 ford taurus. I was told by the dealership after bring my car into the shop four times that my car was "psycho". They had no explanation to why my rpm's in my car where going from 0 to 500 rpm's erratical when in park. After a couple of minutes of my car running rough in park it finally shuts off. Before it shuts off the battery light flashes ( if that has anything to do with it). The third time I brought my car to the dealership they said that it was the alternator going out. They replaced it, yet it still does it. I mainly notice the cars rpms going crazy when the head lamps are on and when my heater and defroster are on. I need help!

 

sounds like idle air control valve .