* Fuel Pump: A failing fuel pump might struggle to keep up with the increased fuel demand at higher speeds. The pump may be weak, or the fuel filter could be clogged, restricting fuel flow. This is a prime suspect.
* Fuel Filter: A clogged fuel filter is a common cause of reduced fuel flow, leading to engine hesitation or stalling, especially under load. It's relatively inexpensive and easy to replace.
* Carburetor Issues (if applicable): If your 305 has a carburetor (less likely in '83 but possible depending on trim), several problems could arise: a clogged jet, a malfunctioning accelerator pump, a worn-out float valve, or a vacuum leak. These affect fuel delivery at various engine loads.
* Ignition System: Problems with the ignition system, such as a failing distributor cap, rotor, spark plug wires, or even the ignition coil, can cause misfires, especially under load when the engine is demanding more power. Misfires reduce power and can lead to a feeling of near-stall.
* Throttle Position Sensor (TPS) or other sensors (if fuel injection): If your Caprice has fuel injection (more likely in '83), a faulty TPS could provide incorrect information to the engine computer, leading to poor fuel delivery. Other sensors like the Mass Airflow Sensor (MAF) or Oxygen Sensor (O2) could also be culprits.
* Vacuum Leaks: Vacuum leaks disrupt the proper mixture of air and fuel, often leading to poor performance and stalling, especially noticeable under load.
* Transmission Issues (less likely): While less probable, a transmission problem could indirectly cause this. If the transmission is slipping or struggling, the engine might be starved of power, leading to a feeling of wanting to shut off.
Troubleshooting Steps:
1. Check the Fuel Filter: This is the easiest and cheapest place to start. Replace it with a new one.
2. Listen for Fuel Pump Noise: With the ignition on (but engine off), listen near the fuel tank for the whirring sound of the fuel pump. If it's weak or absent, the pump is suspect.
3. Inspect Spark Plugs and Wires: Check the spark plugs for fouling or damage, and visually inspect the spark plug wires for cracks or damage.
4. Check for Vacuum Leaks: Visually inspect all vacuum hoses for cracks, splits, or loose connections. A spray bottle with soapy water can help locate leaks.
5. Have it Diagnosed: If you're not comfortable tackling these yourself, take it to a mechanic specializing in older vehicles. They can perform a proper diagnosis using tools and experience to pinpoint the problem.
Addressing the fuel delivery system (pump, filter, carburetor/fuel injection components) should be your first priority. If those check out okay, then delve into the ignition system. Ignoring the issue could lead to more serious engine damage.
