I have a chevy Malibu classic when I take the key out the car is still running and drivable. Sometimes the engine shuts off when I turn it off but the fan and radio is still running does anyone know what's wrong so I can put it in the shop? I don't want to take it to the shop not knowing what's wrong with it and having to pay an arm and a leg. I want to know what's wrong so I can price it before I put it in the shop