* Crankshaft Position Sensor (CKP): This is a common failure point on older vehicles. The CKP sensor tells the computer the crankshaft's position, crucial for proper ignition timing. Heat can cause these sensors to malfunction, leading to stalling. If the signal becomes erratic when hot, the engine won't run smoothly. This is a high probability given the other components have been ruled out.
* Computer (PCM/ECM): While less likely than the CKP, the engine control module itself could be failing due to heat. Internal components can degrade over time and become sensitive to temperature changes. This is harder to diagnose and often requires professional testing.
* Wiring Harness: Check the wiring harness connections to the ignition system, especially around the distributor and coil. Heat can cause wires to short or the insulation to degrade, leading to intermittent connections. Look for any signs of melting or damage.
* Fuel System: While less likely given the symptom description, a heat-sensitive issue in the fuel delivery system (fuel pump, fuel filter, injectors) could be causing fuel starvation when hot. Does the engine crank normally when it stalls, or does it fail to crank? A failing pump might show reduced cranking power when hot due to lack of fuel pressure.
* Cooling System Issues: While less directly related to the stalling, an overheating engine can exacerbate underlying electrical problems. Ensure your cooling system (radiator, thermostat, water pump, coolant level) is functioning correctly. A slightly overheating engine might make an existing problem much worse.
Troubleshooting Steps:
1. Check the CKP sensor: This should be your priority. Test its output signal using a multimeter or a scan tool. A failing sensor will often show intermittent or incorrect signals when hot. Replacement is relatively inexpensive and straightforward.
2. Inspect the wiring harness: Carefully examine all wiring related to the ignition system for any signs of damage, chafing, or loose connections. Pay particular attention to areas exposed to heat.
3. Check fuel pressure: If the engine cranks but doesn't start when hot, have a mechanic check the fuel pressure. A drop in fuel pressure when hot can point to a fuel pump or fuel filter problem.
4. Professional Diagnosis: If you've checked the above and are still having issues, take it to a mechanic with diagnostic equipment. They can use a scan tool to read any error codes stored in the engine control module and test various sensors and components.
Remember safety first! Work on the vehicle in a well-ventilated area and disconnect the negative battery terminal before working on any electrical components. If you're not comfortable working on your vehicle's electrical system, it's best to leave it to a qualified mechanic.
