* Fuel System Problems:
* Fuel pump: A weak or failing fuel pump can't deliver enough fuel under pressure, leading to stalling, especially under load. This is a common culprit in older vehicles.
* Fuel filter: A clogged fuel filter restricts fuel flow, causing similar symptoms.
* Fuel injectors: Clogged or faulty injectors can prevent proper fuel delivery to the engine.
* Fuel pressure regulator: A malfunctioning regulator can cause inconsistent fuel pressure.
* Ignition System Problems:
* Distributor cap and rotor: Worn or cracked components can cause misfires and stalling. (If your engine is distributor-based, check this thoroughly, even if it was part of the tune-up – a visually okay part might still be malfunctioning.)
* Ignition coil: A failing coil won't provide enough voltage to the spark plugs.
* Spark plugs and wires: Worn or damaged spark plugs or wires lead to misfires and poor combustion. Even if *new* ones were installed, a faulty installation is possible.
* Crankshaft Position Sensor (CKP): This sensor tells the engine's computer where the crankshaft is. A faulty CKP sensor can prevent the engine from starting or cause it to stall.
* Other Potential Issues:
* Mass Airflow Sensor (MAF): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can cause erratic engine operation and stalling.
* Throttle Position Sensor (TPS): Provides information about throttle position to the engine's computer. A faulty TPS can cause poor idling and stalling.
* Vacuum leaks: Small vacuum leaks can disrupt the engine's operation and cause stalling. These are often tricky to find and require a careful inspection of all vacuum lines and components.
* Computer Issues (PCM/ECM): While less common, a failing engine control module (PCM or ECM) can cause unpredictable engine behavior, including stalling.
* Transmission Problems (Automatic): If it's an automatic transmission, problems there could manifest as stalling, especially if the engine RPM drops suddenly when shifting.
Troubleshooting Steps:
1. Check Engine Light (CEL): If the CEL is on, have the codes read using an OBD-II scanner. This will give you valuable clues about the problem.
2. Fuel Pressure Test: Have a mechanic test the fuel pressure to rule out fuel delivery problems.
3. Visual Inspection: Carefully inspect all vacuum lines, wiring, and components for damage or leaks.
4. Test Ignition System: Test the ignition coil, spark plugs, and wires.
5. Check MAF and TPS Sensors: These are relatively inexpensive and easy to replace, but a diagnostic scan may indicate if they're actually the problem.
Because this involves multiple systems, it's highly recommended to take the vehicle to a qualified mechanic for proper diagnosis. Trying to fix it yourself without proper tools and experience could lead to further damage or wasted money on unnecessary parts. A diagnostic scan and a thorough inspection are the best first steps.
