Fuel System:
* Clogged fuel filter: Restricts fuel flow to the engine.
* Faulty fuel pump: Inability to deliver sufficient fuel pressure. This is more likely to cause stalling under load (acceleration) than at idle.
* Bad fuel injectors: Clogged or malfunctioning injectors prevent proper fuel delivery.
* Low fuel level: Seems obvious, but sometimes overlooked!
Ignition System:
* Crankshaft Position Sensor (CKP): This sensor tells the engine's computer where the crankshaft is in its rotation. A faulty CKP will cause the engine to stall or not start. This is a very common cause of stalling in older vehicles.
* Cam Position Sensor (CMP): Similar to the CKP, but for the camshaft. A fault can lead to misfiring and stalling.
* Ignition coil: Provides the spark to ignite the fuel-air mixture. A weak or failing coil can cause misfires and stalling.
* Spark plugs and wires: Worn, damaged, or fouled spark plugs or wires will prevent proper ignition.
* Distributor cap and rotor (if applicable): Older vehicles might use these components which can become worn or cracked, interrupting the spark.
Other Potential Causes:
* Mass Airflow Sensor (MAF): Measures the amount of air entering the engine. A faulty MAF sensor can cause incorrect fuel mixture leading to stalling.
* Throttle Position Sensor (TPS): Tells the computer the throttle's position. A faulty sensor can lead to erratic idling and stalling.
* Idle Air Control (IAC) Valve: Regulates airflow at idle. A dirty or malfunctioning IAC valve can cause stalling, especially at idle.
* Vacuum leaks: Leaks in the intake manifold or vacuum hoses can disrupt the engine's air/fuel mixture.
* Alternator: If the alternator isn't charging the battery, the car will eventually stall.
* Battery: A weak battery can also cause stalling, particularly if the engine is under stress.
* Computer Problems (PCM/ECM): Though less common, a faulty engine control module (PCM or ECM) can cause a variety of problems, including stalling.
Troubleshooting Steps:
1. Check the obvious: Fuel level, battery voltage, and any visible damage to wiring or hoses.
2. Listen for unusual sounds: Clicking, ticking, or grinding noises can indicate a specific problem.
3. Check engine codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the engine computer. This can pinpoint the problem area.
4. Visual inspection: Carefully examine all components mentioned above for visible signs of damage or wear.
Because there are so many potential causes, it's highly recommended to have a qualified mechanic diagnose the problem. Trying to troubleshoot this yourself without the proper tools and knowledge could lead to further damage or wasted time and money.
