Fuel System:
* Fuel Pump: A weak or failing fuel pump might provide enough pressure to start the engine, but not sustain it once running. The pump could be wearing out, or there might be a blockage in the fuel line.
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to similar symptoms.
* Fuel Pressure Regulator: This regulates fuel pressure. A faulty regulator could cause inconsistent fuel pressure, leading to the engine stalling.
* Crankshaft Position Sensor (CKP): While related to ignition timing, a faulty CKP can indirectly affect fuel delivery because the engine computer needs this signal to control fuel injection.
Ignition System:
* Ignition Coil: The coil provides the high voltage needed for the spark plugs. A failing coil might initially work but then give out after a few seconds.
* Distributor (if equipped): Older vehicles may have distributors. Issues with the distributor cap, rotor, or points (if equipped) can interrupt the spark.
* Spark Plugs/Wires: Worn or fouled spark plugs or damaged wires can cause misfires and stalling.
* Camshaft Position Sensor (CMP): Similar to the CKP, the CMP is crucial for ignition timing.
* Mass Airflow Sensor (MAF): A dirty or faulty MAF sensor can provide incorrect information to the engine computer, leading to improper fuel and ignition timing.
Other Possibilities:
* Idle Air Control (IAC) Valve: This controls the idle speed. A malfunctioning IAC valve might not be able to maintain the engine speed after starting.
* Throttle Position Sensor (TPS): A faulty TPS could be sending inaccurate readings to the engine computer, causing it to shut down.
* Computer/PCM (Powertrain Control Module): Though less likely, a failing PCM could be responsible. This is usually diagnosed last after other components are checked.
* Battery/Alternator: While unlikely to cause a 5-second stall specifically, a weak battery or alternator could be contributing factors if the voltage drops suddenly.
Troubleshooting Steps:
1. Check for error codes: Use a code reader (OBD I scanner for a 1990 model) to see if the car's computer has stored any diagnostic trouble codes (DTCs). This can pinpoint the problem area.
2. Listen for the fuel pump: When you turn the key to the "on" position (but before starting), you should hear the fuel pump briefly prime. If you don't hear it, the pump could be bad.
3. Check fuel pressure: This requires a fuel pressure gauge and is best done by a mechanic.
4. Inspect spark plugs and wires: Look for visible damage, wear, or fouling.
5. Check the battery terminals and cables: Ensure they are clean and tight.
Because this is an older car, many components might be worn out. A qualified mechanic familiar with older vehicles will be best equipped to diagnose the issue. Start with the easier checks (fuel pump sound, spark plugs, battery), then move on to more involved diagnostics if needed.
