Don't worry about paying until we get you fixed and back on the road. Even then, this is a free website, so you don't have to. It just helps keep things going.
As far as your problem, I believe you have a bad Idle Air Control solenoid, (IAC). In the newer cars, the throttle plate closes completely at an idle. However, the engine still needs air to run. The IAC is an electronic solenoid that is mounted on the throttle body. Based on information from the car's computer, the IAC determines how much air the engine needs to idle.
When you turn the AC on, automatically, the computer is designed to increase the vehicle idle due to the added load on the engine. Thus, in this case, it is keeping the engine running.
To check the IAC, remove it. Two screws hold it in place. At the end that pushes into the throttle body is a pintel valve. Have a helper turn the key on and off while you watch the pintil valve. It should move (slightly) in and out. If it doesn't, it is bad.
Let me know if you have other questions.
Friday, December 9th, 2011 AT 2:56 AM