Classic/Antique Car Repair: idle 2000 gt mustang 4.6, throttle valves, computer operation

Question
my 2000 gt mustang 4.6,runs an idles normally,when you turn on the heater or the air condition,then the idle goes up an down an will try to cut off when sitting still.as soon as you cut the heat or air off the idle is fine.have any idea whats causing that.thanks  ronnie  

Answer
You are going to have to get into the computer operation and the sensors on this one. When you throw a load on the engine like the A/C the computer sensor read the load. It then askes the computer to increase throttle opeing by opening an air valve to increase engines power. Some where along this line there is a glitch. It could be as simple as cleaning the throat of the ar intake where the throttle valves are or getting a scanner on the system to check the sensors and the computer.
Brad