* Idle Air Control (IAC) Valve: This valve regulates the amount of air entering the engine at idle. A dirty or faulty IAC valve can't maintain the proper idle speed, causing the engine to stall when the throttle is released. This is the most common cause of this problem.
* Throttle Position Sensor (TPS): This sensor tells the computer the position of the throttle. A faulty TPS can provide incorrect information, leading to the engine stalling. The computer might be cutting fuel because it thinks the throttle is closed, even though it isn't.
* Vacuum Leaks: Cracks or holes in vacuum hoses can disrupt the air/fuel mixture, leading to unstable idling and stalling. Inspect all vacuum hoses for cracks, especially those connected to the intake manifold and brake booster.
* Mass Air Flow (MAF) Sensor: This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can give inaccurate readings, causing poor fuel delivery and stalling.
* Fuel Delivery Issues: While less likely given the symptom (starting but immediately dying), a weak fuel pump or clogged fuel filter could cause insufficient fuel delivery at idle, resulting in stalling.
* Engine Coolant Temperature (ECT) Sensor: A faulty ECT sensor can provide inaccurate readings to the computer, affecting the fuel mixture, particularly during cold starts. This might be more of a factor if the stalling is more pronounced when the engine is cold.
Troubleshooting Steps:
1. Check for Vacuum Leaks: Visually inspect all vacuum hoses for cracks, loose connections, or damage. Listen carefully for hissing sounds near the intake manifold.
2. Clean the IAC Valve: This is often the easiest and most effective first step. Locate the IAC valve (usually near the throttle body), remove it, and clean it thoroughly with carburetor cleaner. Be careful not to damage the delicate parts inside.
3. Check the TPS: You might need a multimeter to check the voltage output of the TPS. Consult a repair manual for specific voltage readings.
4. Clean the MAF Sensor: Use MAF sensor cleaner to gently clean the sensor element. Avoid touching the sensor element directly.
5. Check the Fuel Filter: Consider replacing the fuel filter as a preventative measure.
If you're not comfortable working on your car yourself, it's best to take it to a qualified mechanic. They'll have the diagnostic tools and expertise to pinpoint the exact cause and perform the necessary repairs. Describing the symptoms ("starts but dies when I release the gas pedal") will help them quickly focus their diagnosis.
