* Fuel Delivery Problems (Heat Soak): This is a very common cause. As the engine heats up, components like the fuel pump, fuel injectors, or fuel lines can become less efficient. The fuel might vaporize more readily in the lines, leading to fuel starvation when the engine is hot. A failing fuel pump is particularly susceptible to this. The pump might work fine when cold but struggle to maintain pressure when hot.
* Ignition System Issues: Heat can affect the ignition coil, distributor cap (if equipped), rotor, and spark plug wires. A failing component might only manifest its problem when under heat stress. Weak sparks under heat load can cause misfires and stalling.
* Cooling System Issues: While it seems counterintuitive, a cooling system problem can indirectly cause this. If the engine is overheating (even slightly), it can cause the engine to malfunction in ways that lead to stalling. Check your coolant level, look for leaks, and consider a thermostat check. An overheating engine can also damage other parts.
* Sensor Problems: Various sensors, like the crankshaft position sensor (CKP), coolant temperature sensor (CTS), or air flow meter (AFM/MAF), can malfunction when hot. The engine relies on these sensors for proper operation, and an inaccurate reading can lead to stalling. The CTS is a likely suspect as it directly affects the fuel/air mixture calculations.
* Vacuum Leaks: A vacuum leak can worsen with heat. Hoses can become brittle and crack, causing a loss of vacuum that disrupts the engine's operation. The leak may only become significant when things expand with heat.
Troubleshooting Steps:
1. Check coolant levels and look for leaks: Rule out overheating as a contributing factor.
2. Check the fuel system: Listen for the fuel pump's prime when you turn the ignition on. A weak or failing pump is a prime suspect. Consider checking fuel pressure (requires a gauge).
3. Inspect the ignition system: Check the distributor cap, rotor, and spark plug wires for cracks or signs of wear (if equipped). Consider testing the ignition coil.
4. Check the sensors: A professional mechanic can test the sensors with a scan tool or multimeter. The coolant temperature sensor is a likely starting point.
5. Listen for unusual noises: A ticking, knocking, or hissing sound could indicate a mechanical problem.
6. Inspect vacuum lines: Look for cracks, leaks, or loose connections in the vacuum hoses.
Because this problem only surfaces when the engine is warm, the heat-related issues listed above are the most likely culprits. A mechanic with experience in older vehicles will likely be able to diagnose the problem more efficiently, especially if you can describe the exact conditions when the car stalls (how long it runs after starting, if it's idling or under load, etc.). Trying to diagnose this yourself without the proper tools can be challenging and potentially risky.
