I have a 2006 mazda 3 touring with 80 k miles on it. No real problems so far except last two days when I turn on my heater the engine stalls. What does that mean? There is an audible rattle that sounds like it could be a muffler issue? Weird things is the heater will only stall the car if it is turned to the feet only. I can have the heater on if it is on face only.