Idle System Problems:
* Idle Air Control (IAC) Valve: This valve regulates the amount of air entering the engine at idle. A dirty, sticking, or faulty IAC valve is a very common cause of stalling at idle. It might be letting in too little air when the engine is cold and struggling to maintain idle speed.
* Throttle Position Sensor (TPS): This sensor tells the computer the position of the throttle. A faulty TPS can provide inaccurate readings, leading to improper fuel delivery at idle. A bad TPS can cause erratic idling or stalling.
* Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can provide incorrect readings, leading to a lean or rich fuel mixture, causing stalling, especially at idle.
* Vacuum Leaks: Leaks in the vacuum system can disrupt the idle system's operation. Check all vacuum hoses for cracks, splits, or loose connections. Pay close attention to hoses connected to the brake booster, PCV valve, and other idle-related components.
Fuel Delivery Issues:
* Fuel Pressure Regulator: A faulty fuel pressure regulator might not maintain proper fuel pressure at idle, leading to stalling.
* Fuel Filter: A clogged fuel filter can restrict fuel flow, especially at low engine speeds.
* Fuel Pump: While less likely to cause stalling only at idle, a weak fuel pump might struggle to provide enough fuel under low demand conditions.
Other Possibilities:
* Ignition System: While less common in this scenario, a weak ignition coil or failing spark plugs/wires could cause misfires at idle, leading to stalling.
* Computer (PCM): A faulty engine control module (PCM) is a less likely but possible cause. This would require diagnostic testing.
* Crankshaft Position Sensor (CKP): A faulty CKP sensor can disrupt the engine's timing, possibly leading to stalling, though this is more likely to cause problems across the rev range.
Troubleshooting Steps:
1. Check for obvious vacuum leaks: Visually inspect all vacuum hoses.
2. Clean the IAC valve: This is a relatively easy and inexpensive first step.
3. Check the MAF sensor: Clean it carefully with MAF sensor cleaner (avoid touching the sensor element).
4. Check the TPS: This often requires a multimeter to check its voltage output.
5. Check fuel pressure: This requires a fuel pressure gauge and is best done by a mechanic.
Important Note: Without proper diagnostic tools and some mechanical knowledge, troubleshooting these issues can be challenging. If you're not comfortable working on your car yourself, it's best to take it to a qualified mechanic for diagnosis and repair. They'll have the tools and expertise to pinpoint the exact cause of the problem efficiently.
