If you mean that it shuts off while idling it could be a bad Intake Air Control (IAC) valve. Very easy to replace and costs about $50. See detailed instructions at Autoclinix.com on how to replace it...
Passenger side of the car, near back door / back tire, mounted up on the frame rail or just inside the body mount. There is a box with 2 screws and a rubber hose running in one side and out the...