* Fuel Delivery Issues:
* Fuel Pump: Heat can cause a weak fuel pump to fail or become less efficient. It might deliver enough fuel at lower temperatures but struggle under high heat, leading to stalling.
* Fuel Filter: A clogged fuel filter restricts fuel flow, and this is exacerbated by the increased viscosity of fuel in hot weather.
* Fuel Injectors: Heat can cause fuel injectors to malfunction, delivering an inconsistent or insufficient fuel spray. This is less likely to cause a complete stall, but could contribute to the problem.
* Vapor Lock: While less common in fuel-injected systems, vapor lock can still occur. Heat can vaporize fuel in the lines, preventing liquid fuel from reaching the engine.
* Ignition System Problems:
* Ignition Coil: Heat stress can weaken the ignition coil's ability to generate the necessary spark.
* Distributor Cap and Rotor (if applicable): Cracks or worn components in the distributor can cause misfires, especially under heat stress. (Less likely on a '94, as many used electronic ignition.)
* Ignition Module/Control Module: Electronic components can fail due to heat. This is more likely a cause if the engine struggles to restart immediately after stalling.
* Sensor Issues:
* Crankshaft Position Sensor (CKP): A faulty CKP sensor can prevent the engine from receiving the signal to fire, especially if heat is affecting its operation.
* Mass Airflow Sensor (MAF): A failing MAF sensor can cause poor fuel mixture, leading to stalling under stress.
* Electrical Problems:
* Loose or Corroded Connections: Heat can expand and contract wiring, leading to loose connections or increased resistance in circuits.
* Alternator: While not directly causing a stall, a failing alternator could drain the battery, leading to electrical failures that result in stalling.
Troubleshooting Steps:
1. Check for error codes: Use an OBD-II scanner to check for any diagnostic trouble codes (DTCs). This is the first and most important step.
2. Examine fuel pressure: Have a mechanic check fuel pressure when the engine is hot to rule out fuel pump or filter issues.
3. Inspect ignition components: Visually inspect the ignition coil, distributor cap and rotor (if applicable) for signs of damage or wear.
4. Check sensors: Test the CKP and MAF sensors for proper operation, especially when the engine is hot.
5. Look for loose or corroded wiring: Inspect the wiring harness, particularly in areas exposed to heat.
6. Test the alternator: Ensure the alternator is charging the battery correctly.
Important Note: Since the issue only occurs after prolonged driving in high heat, focusing on components susceptible to heat stress is crucial. It's best to have a qualified mechanic diagnose the problem, as pinpointing the exact cause can be challenging without proper testing equipment.
