I. Fuel System:
* Fuel Pump: A failing fuel pump can't deliver enough fuel pressure. You'll need a fuel pressure gauge to test this. Low pressure indicates a pump problem (it could be the pump itself, the fuel filter, or a clogged fuel line).
* Fuel Filter: A clogged fuel filter restricts fuel flow. Replacing the filter is relatively inexpensive and easy. Do this *before* suspecting the fuel pump.
* Fuel Injectors (if equipped): While less likely on an '84 Caprice (which may have a carburetor), if it has fuel injection, clogged or failing injectors can prevent proper fuel delivery. Testing requires specialized tools.
* Carburetor (if equipped): If it's carbureted, numerous problems can cause stalling. This requires carburetor cleaning, rebuilding, or replacement, potentially involving adjustments to the idle mixture screws and float level. A mechanic experienced with carburetors is often best suited for this.
II. Ignition System:
* Ignition Coil: A failing coil won't produce the necessary high voltage to spark the plugs. Testing involves checking for spark at the plugs using a spark tester.
* Distributor Cap and Rotor: Corrosion or wear can interrupt the spark delivery. Inspection and replacement are relatively simple.
* Ignition Switch: A faulty ignition switch might not provide consistent power to the ignition system. This is harder to diagnose and may require testing with a multimeter.
* Pick-up Coil (in the distributor): This component sends the signal to the ignition module to trigger the spark. A faulty pickup coil will prevent the engine from running consistently.
III. Other Potential Causes:
* Idle Air Control (IAC) Valve (if equipped): This valve controls airflow at idle. A dirty or faulty IAC valve can lead to stalling. Cleaning or replacement might be necessary.
* Throttle Position Sensor (TPS) (if equipped): If equipped, a faulty TPS provides incorrect information to the engine control unit (ECU), leading to erratic idle and stalling.
* Vacuum Leaks: Leaks in the vacuum lines can disrupt the engine's operation, leading to stalling. Inspect all vacuum lines for cracks or loose connections.
* Battery and Alternator: A weak battery or failing alternator can cause intermittent power problems, resulting in stalling. Test the battery voltage and the alternator's charging output.
* Engine Temperature Sensor: An inaccurate engine temperature sensor can cause the ECU to provide incorrect fuel and ignition timing, leading to stalling.
* Computer Issues (ECM): While less common, a failing engine control module (ECM) can cause a variety of problems, including stalling. This is the most difficult to diagnose and often requires specialized equipment.
How to Approach Diagnosis:
1. Start Simple: Begin with the easiest and cheapest checks: fuel filter, visually inspect vacuum lines, check battery voltage.
2. Gather Information: Note when the stalling happens (immediately after starting, after warming up, only when idling, etc.). This helps narrow down the possibilities.
3. Systematic Testing: Follow a logical sequence based on the most likely causes (fuel system first, then ignition).
4. Use a Multimeter: A multimeter is invaluable for testing battery voltage, alternator output, and checking for power at various points in the ignition and fuel systems.
5. Consult a Repair Manual: A Haynes or Chilton repair manual for your specific vehicle will provide diagrams, specifications, and troubleshooting guides.
6. Seek Professional Help: If you're not comfortable working on your car's electrical or fuel systems, it's best to consult a mechanic. Attempting repairs without the proper knowledge and tools can lead to further damage.
Remember safety first! Disconnect the negative battery terminal before working on any electrical components. If you're not experienced with car repair, don't hesitate to seek professional assistance. This is just a general guide; the specific cause will vary depending on your car's condition and history.
