* Ignition Control Module (ICM): This is a frequent suspect in older GM vehicles. The ICM can fail when it gets hot. It controls the ignition system, so a failing ICM will often cause the engine to die once it reaches operating temperature.
* Distributor: Issues within the distributor itself, such as worn-out components or a failing pickup coil, could also be to blame. While you say you're getting spark, the *strength* of the spark could be affected by a failing distributor.
* Temperature Sensor: A faulty coolant temperature sensor (CTS) can provide incorrect readings to the engine control unit (ECU). This could lead to improper fuel delivery or ignition timing once the engine warms up, causing it to stall.
* Fuel Pump Relay: Although less likely given that it runs initially, a relay that fails when hot could interrupt power to the fuel pump.
* Mass Airflow Sensor (MAF) or Throttle Position Sensor (TPS): Problems with these sensors, which measure airflow and throttle position, could cause issues once the engine warms up and operating conditions change.
Troubleshooting Steps:
1. Check for consistent spark: While you say you have spark, verify it's a strong spark at all RPMs *after* the engine warms up and stalls. A weak spark won't be sufficient to ignite the fuel properly.
2. Inspect the ICM: Visually check the ICM for any signs of damage or overheating.
3. Test the coolant temperature sensor: This is usually a relatively inexpensive and easy test. You can do this yourself with a multimeter, or a mechanic can easily do it.
4. Check fuel pressure: Measure fuel pressure when the engine is cold and then again after it warms up and stalls. This will help rule out fuel delivery problems.
5. Inspect the distributor cap and rotor: Look for cracks, arcing, or wear and tear.
Given the age of the vehicle, it's often advisable to replace parts known to fail due to heat rather than chasing a more elusive electrical fault. The ICM is a good place to start.
It's best to consult a mechanic or experienced automotive technician for a proper diagnosis if you're not comfortable working on the vehicle yourself. They have the tools and expertise to accurately pinpoint the issue.
