Greetings!
What an unusual symptom; congratulations on being observent enough to notice the connection between the stalling and the defogger operation...
After discussing the symptom amongst ourselves, we believe you have a base idle speed problem in the vehicle. When a heavy electrical load such as a defogger grid is turned on, the usual result is that the alternator becomes harder to turn because it is being asked to generate more amperage to keep up with the demand. The engineers that design the vehicel take this into account, and design the vehicle's software to compensate by increasing idle speed when a heavy load is placed on the electrical system. It would appear that when the powertrain controller is commanding a higher than normal idle speed, the vehicle operates normally. By this reasoning, it would seem that your base (unloaded) idle speed may be below specs.
Idle speed is not adjustable on this vehicle; it is controlled by means of an idle air control valve that bleeds air around the throttle plate. The PCM commands the valve to open longer for increased idle speed, and to close to reduce idle speed. When the system is designed, it is assumed that a certain amount of minimum airflow will take place inside the throttle bore, through the small gap between the throttle plate and the walls of the throttle body. If this minimum airflow is restricted, it will result in incorrect IAC valve position calculation by the PCM. I would suggest inspecting the inside of the throttle bore for deposits which may be reducing airflow; expecially in the throttle plate area. If you find such deposits, tehy can be removed by using a solvent such as berkebile 2+2 gum cutter and an old toothbrush. If this is not effective at resolving the issue, you may have an IAC valve not responding to commands as it should.
If the throttle body cleaning does not help, I would suggest taking the vehicle in to a shop equipped with a scan tool capable of reading live engine data on theis vehcile. usually idle concerns are pretty quick and easy to diagnose with the right equipment, and therefore are usually fairly inexpensive to repair.
I hope this is helpful; if so, an accept would be most appreciated! Thanks!
