Here's a systematic approach to troubleshooting your 1993 Chevy Caprice Classic stalling problem:
1. Verify the work you've already done:
* Fuel Pump: While you replaced it, ensure it's receiving power and is actually pumping fuel. You might need a fuel pressure gauge to check the pressure at the fuel rail. Low pressure or no pressure points to a fuel delivery problem beyond the pump itself (e.g., clogged fuel filter, faulty fuel pressure regulator).
* Computer (ECM): Was the ECM actually faulty, or did you replace it as a shot in the dark? If it was replaced, was it a remanufactured or new unit, and was it programmed correctly for your car? A bad remanufactured ECM is possible.
* Ignition System: Even with new parts, double-check:
* Proper gap on spark plugs: Incorrect gap can cause misfires and stalling.
* Distributor timing: Is the distributor properly aligned? A slightly off timing can cause running issues. This requires a timing light.
* Spark plug wires routed correctly: Make sure they're on the correct cylinders and aren't arcing against anything.
* Coil: Although you replaced the cap and rotor, the ignition coil itself could be weak or failing.
2. Areas to investigate further:
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A failing CKP sensor can cause intermittent stalling, especially when the engine is warm or under load.
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle position. A faulty TPS can cause erratic idling and stalling.
* Mass Airflow Sensor (MAF): Measures the amount of air entering the engine. A dirty or faulty MAF sensor can lead to a lean fuel mixture and stalling. Try cleaning it with MAF sensor cleaner (following the instructions carefully).
* Idle Air Control (IAC) valve: Regulates airflow at idle. A dirty or faulty IAC valve can cause stalling, especially at idle. Cleaning it is often a good first step.
* Vacuum Leaks: Check all vacuum lines for cracks, leaks, or disconnections. Even a small leak can disrupt engine operation. Spray some carb cleaner around suspected areas and listen for a change in engine speed. (Be careful with open flames and this method).
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to stalling. It's a cheap and easy part to replace, even if you recently replaced the fuel pump.
* Ignition Switch: A failing ignition switch can interrupt power to various components, causing stalling.
3. Diagnostic Tools:
* OBD1 Scanner (for your 1993 Caprice): This is crucial. It will read trouble codes from your car's computer, giving you clues about what's wrong. You can find OBD1 scanners relatively inexpensively online. Without it, you're essentially working in the dark.
* Fuel Pressure Gauge: As mentioned above, this is essential for verifying fuel pressure.
4. Professional Help:
If you've checked all the above and are still stumped, it's time to consider taking your Caprice to a qualified mechanic. They have the diagnostic equipment and expertise to pinpoint the problem more efficiently.
Remember to be methodical and systematic in your approach. Tackling one area at a time, and verifying your work at each step, will increase your chances of finding and fixing the problem. The OBD1 code reader is a vital step you shouldn't skip.
