Hi , I'm new to forum. I have a 99 A6 Quatro 2.8 and my problem is she runs great until I turn the a/c or heater off. When I turn them off it will continue to run until I slow down enough to make a turn and then it will shut down. So far, I have been lucky that I haven't been hit. Any advise would be helpful. Does anyone out there have a clue to this problem?????