Here's a breakdown of potential causes:
* ECM Failure (Heat-Related): The ECM might have a failing component that's sensitive to heat. The initial startup is successful, but as the ECM warms up, the problem manifests, causing the engine to stall.
* Sensor Issues: Several sensors provide crucial data to the ECM:
* Crankshaft Position Sensor (CKP): A faulty CKP can cause intermittent starting issues. If it fails after the engine warms up, that could explain your problem.
* Coolant Temperature Sensor (CTS): The ECM uses this sensor to adjust fuel mixture. A faulty CTS could lead to improper fueling after a minute or so of running.
* Throttle Position Sensor (TPS): A failing TPS could cause erratic idle or stalling, more likely after the engine warms up.
* Mass Airflow Sensor (MAF): While less common to cause an immediate stall, a failing MAF can cause similar issues.
* Ignition System Issues: Although less likely given the restart ability, a failing ignition component (ignition coil, ignition module) that's heat-sensitive could be a possibility.
* Wiring Harness Issues: A short circuit or a corroded connection somewhere in the wiring harness could create problems that worsen with heat.
* Other Problems: While less probable given the info, there's always the possibility of something like a vacuum leak that worsens as things heat up.
Troubleshooting Steps:
1. Check the obvious: Ensure battery terminals are clean and tight. Check all fuses and relays associated with the fuel system and ignition.
2. Check and Clean Connectors: Examine all connectors going to the ECM, CKP, CTS, TPS, MAF, and ignition components for corrosion or loose connections. Clean them with electrical contact cleaner.
3. Sensor Testing: The most effective method is to use a multimeter to test the sensors to see if they are providing the correct resistance values according to the specifications in your truck's repair manual. You may need to have them tested at an auto parts store.
4. Scan Tool: Use an OBD-II scan tool (if your truck has one) to read any diagnostic trouble codes (DTCs). This can pinpoint potential problems. Since this is a 93, it likely won't have OBD-II. A mechanic's scan tool is more likely to be successful here.
5. Professional Diagnosis: If you're not comfortable doing this, take it to a qualified mechanic. They have the tools and expertise to diagnose the problem properly. Explaining the exact symptoms will help them narrow down the possibilities.
The fact that it restarts indicates the ECM is *probably* not completely fried, but a failing component within the ECM or something it's monitoring is much more likely.
