Fuel System:
* Fuel Pump: A failing fuel pump can't deliver enough fuel to the engine, causing it to stall, especially under load (acceleration or hills).
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to similar symptoms as a bad fuel pump.
* Fuel Injectors: Clogged or failing injectors can prevent proper fuel delivery to the cylinders.
* Fuel Pressure Regulator: A malfunctioning regulator can cause incorrect fuel pressure, leading to inconsistent running or stalling.
Ignition System:
* Distributor Cap and Rotor: Worn or damaged components can cause misfires or complete engine failure. Common in older vehicles.
* Ignition Coil: A failing coil won't produce the necessary high voltage to ignite the spark plugs.
* Spark Plugs and Wires: Worn or damaged spark plugs and wires can lead to misfires and stalling.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A faulty sensor prevents the engine from firing.
* Cam Position Sensor (CMP): Similar to the CKP sensor, a faulty CMP prevents proper ignition timing.
Other Potential Causes:
* Alternator: If the alternator fails, the battery will eventually drain, causing the engine to die.
* Battery: A weak or dying battery can leave the car stranded.
* Mass Airflow Sensor (MAF): A faulty MAF sensor provides inaccurate air readings to the computer, leading to poor running and stalling.
* Throttle Position Sensor (TPS): Similar to the MAF, a bad TPS provides incorrect information to the computer about throttle position.
* Temperature Sensor: An inaccurate temperature reading can cause the computer to make poor fuel and ignition adjustments.
* Computer Problems: While less common, a failing engine control module (ECM) can lead to all sorts of erratic behavior.
* Overheating: The engine overheating can cause it to shut down to prevent damage. Check the coolant level.
* Vacuum Leaks: Leaks in the vacuum system can disrupt engine operation.
Troubleshooting Steps:
Since there are so many possibilities, systematic troubleshooting is crucial. Start with the simpler checks:
1. Check the obvious: Battery terminals (corrosion?), coolant level, oil level.
2. Listen for unusual sounds: Any knocking, grinding, or whining sounds can provide clues.
3. Check the fuses and relays: A blown fuse or relay can cut power to essential components.
4. Scan the codes: If you have a code reader, scan the car's computer for diagnostic trouble codes (DTCs). This will often pinpoint the problem area.
Without more information about the circumstances of the stalling (e.g., did it happen suddenly? Was there any warning signs? Did it restart easily?), pinpointing the exact cause is difficult. If you're not comfortable working on cars yourself, it's best to take it to a mechanic.
