* Fuel System Issues: This is often the primary suspect.
* Fuel Pump: A failing fuel pump might not supply enough fuel, especially under load (going uphill or accelerating). It could be weak, clogged, or the pump relay might be failing.
* Fuel Filter: A clogged fuel filter restricts fuel flow, leading to engine starvation. This is a cheap and easy thing to check/replace first.
* Fuel Injectors (if equipped): While less common on an '84, if it has fuel injection, clogged or failing injectors can cause intermittent power loss. Carburetors (more likely on an '84) can also become clogged or have issues with the float level.
* Fuel Lines/Hoses: Cracks or leaks in fuel lines can cause fuel starvation.
* Ignition System Problems:
* Distributor Cap and Rotor: Worn or damaged components can cause poor spark delivery, resulting in misfires and stalling.
* Ignition Coil: A failing coil won't provide enough voltage to the spark plugs.
* Spark Plugs and Wires: Worn or damaged spark plugs and wires can lead to misfires. These are relatively inexpensive to replace.
* Ignition Module (or TFI module): This is a common failure point in older Ford vehicles. It controls the ignition system and a faulty module can cause all sorts of problems.
* Vacuum Leaks: A significant vacuum leak can disrupt the engine's air-fuel mixture, leading to stalling. Check all vacuum hoses for cracks, holes, or loose connections.
* Electrical Issues:
* Alternator: A failing alternator won't charge the battery, leading to a sudden power loss. Check the battery voltage while the engine is running.
* Battery Connections: Corroded or loose battery terminals can interrupt the electrical flow. Clean them thoroughly.
* Wiring Harness: Worn or damaged wiring in the engine bay can cause intermittent problems.
* Sensor Problems:
* Throttle Position Sensor (TPS) (if equipped): A faulty TPS can provide inaccurate information to the engine control unit (ECU), leading to poor fuel mixture and stalling. More likely on fuel injected models.
* Other Sensors: Various other sensors (e.g., oxygen sensor, crankshaft position sensor) can cause problems, but these are less likely to cause a sudden cut out.
Troubleshooting Steps:
1. Start with the simplest and cheapest: Check the fuel filter, spark plugs, and wires. Inspect all vacuum lines. Clean battery terminals.
2. Check the fuel pressure: If you have the tools, measure the fuel pressure to see if the pump is delivering sufficient fuel.
3. Listen for unusual sounds: Pay attention to any unusual noises from the engine, especially while it's cutting out.
4. Inspect the distributor: Check the cap and rotor for wear or damage.
5. Test the battery voltage: Ensure the alternator is charging the battery properly.
6. Consult a repair manual: A factory service manual for your 1984 Ford F-150 will provide detailed information on diagnosing and repairing the various systems.
If you're not comfortable working on your vehicle yourself, take it to a qualified mechanic for diagnosis and repair. The problem could be anything from a simple fix to something more complex, and a professional can quickly pinpoint the cause. Don't continue driving the truck if it's cutting out unexpectedly – it could be dangerous.
