High-Probability Causes:
* Crankshaft Position Sensor (CKP Sensor): This sensor tells the computer the position of the crankshaft. A faulty CKP sensor will prevent the engine from receiving the signal it needs to continue firing, leading to a sudden stall. This is a very common cause of this problem.
* Cam Position Sensor (CMP Sensor): Similar to the CKP sensor, a bad CMP sensor disrupts the engine's timing, causing it to stall.
* Fuel Pump: A failing fuel pump may not provide sufficient fuel pressure at higher speeds or under load. The engine might run fine at idle but die under stress. Listen for the fuel pump whirring when you turn the key to the "on" position – if you don't hear it, that's a strong indication of a problem.
* Ignition System: Problems with the ignition coil, ignition module, distributor cap (if equipped), or rotor can interrupt the spark to the plugs, causing the engine to stall. Worn spark plugs or plug wires are also possibilities.
* Mass Airflow Sensor (MAF Sensor): A dirty or faulty MAF sensor provides inaccurate readings to the engine computer, leading to improper fuel mixture and potential stalling.
Less-Likely, But Still Possible Causes:
* Throttle Position Sensor (TPS): An inaccurate TPS reading can cause the engine to misfire or shut down.
* Computer/PCM (Powertrain Control Module): Though less common, a faulty PCM can cause a wide range of problems, including stalling. This is usually diagnosed last.
* Alternator: A failing alternator won't charge the battery, and once the battery is drained, the engine will die. Check your battery voltage.
* Fuel Filter: A clogged fuel filter restricts fuel flow, causing similar symptoms to a failing fuel pump.
* Wiring Issues: Damaged or corroded wiring can interrupt the signal to crucial components. Look for any obvious signs of damage in the engine bay.
Troubleshooting Steps:
1. Check the obvious: Look for any warning lights on the dashboard (Check Engine Light, battery light).
2. Listen for the fuel pump: Turn the ignition key to the "on" position (without starting the car) and listen for the fuel pump whirring.
3. Check the battery voltage: A low voltage indicates a charging system problem (alternator).
4. Check the spark: A simple spark test on the spark plugs can help rule out ignition issues. Caution: High voltage!
5. Get the codes read: Use a OBD-II scanner to retrieve any diagnostic trouble codes (DTCs) stored in the PCM. This will give you valuable clues about the problem. Auto parts stores often offer this service for free.
Recommendation:
Given the potential safety risks, I strongly recommend having a qualified mechanic diagnose this problem. Ignoring a stalling engine while driving is dangerous. The information above is for educational purposes only and should not be considered a substitute for professional automotive repair.
