Fuel System:
* Fuel Pump Failure: A weak or failing fuel pump can't supply enough fuel under the increased demand of acceleration. This is a common cause.
* Clogged Fuel Filter: A dirty filter restricts fuel flow, leading to starvation under load.
* Carburetor Issues (if applicable): If it's a carbureted engine, problems include:
* Clogged jets: Restrict fuel flow.
* Diaphragm leaks: Affect fuel metering.
* Float level issues: Incorrect fuel level in the bowl.
* Accelerator pump problems: Fails to provide the extra fuel needed for acceleration.
* Fuel Pressure Regulator (if applicable): A faulty regulator can deliver incorrect fuel pressure.
* Bad Fuel Lines/Leaks: Cracks or holes in the fuel lines will cause fuel starvation.
* Dirty Fuel: Water or debris in the fuel tank can clog the system.
Ignition System:
* Distributor Issues: Worn points (if equipped), faulty condenser, failing rotor, or worn distributor cap can cause intermittent spark.
* Worn Spark Plugs/Wires: Misfires under load are common.
* Ignition Coil Problems: A weak coil can't provide enough voltage for a strong spark.
* Ignition Module (Electronic Ignition): Failure of the electronic control unit can disrupt ignition timing.
Airflow/Exhaust:
* Clogged Air Filter: Restricts airflow, leading to a lean condition and potential stall.
* Vacuum Leaks: Leaks in the intake manifold or vacuum lines disrupt the air/fuel mixture.
* Exhaust Restriction: A severely clogged exhaust system can back up pressure and choke the engine.
Other Possibilities:
* Overheating: The engine may be overheating and cutting out for safety. Check coolant levels and look for signs of overheating.
* Electrical Problems: A faulty connection or wiring harness can interrupt power to essential components.
* Transmission Issues (Automatic): Although less likely to cause a sudden cutout, problems within the automatic transmission can impact engine performance.
Troubleshooting Steps:
1. Start with the basics: Check fuel level, air filter, and obvious vacuum leaks.
2. Listen carefully: Is there a sputtering sound, a backfire, or just a complete cut-out? This can give clues.
3. Check for codes: If it has an electronic ignition system, a check engine light might provide diagnostic codes.
4. Systematic approach: Tackle the fuel system first (pump, filter, pressure), then move to ignition, and finally airflow/exhaust.
A mechanic familiar with Ford 390 engines will be able to diagnose the problem more quickly and efficiently. The age and condition of the engine will also influence the likely culprit.
