Fuel System:
* Dirty Fuel Filter: A clogged fuel filter restricts fuel flow, leading to hesitation and stumbling. This is a cheap and easy first check.
* Bad Fuel Pump: A weak or failing fuel pump can't supply enough fuel under acceleration. You might hear a whining noise from the fuel tank if it's failing.
* Clogged Fuel Injectors: Clogged injectors prevent proper fuel delivery to the cylinders. This often manifests as rough running and hesitation. Cleaning or replacing them might be necessary.
* Low Fuel Pressure: Problems with the fuel pressure regulator can cause inconsistent fuel pressure.
* Bad Fuel: Contaminated or low-quality fuel can cause all sorts of problems, including stumbling. Try a different gas station.
Ignition System:
* Worn Spark Plug Wires: Cracked or damaged wires can cause misfires, leading to a rough running engine.
* Failing Ignition Coil: A weak or faulty coil won't provide enough spark to ignite the fuel-air mixture consistently.
* Bad Spark Plugs: Worn, fouled, or improperly gapped spark plugs are a common cause of misfires.
* Distributor Cap and Rotor (if applicable): These components can wear out, leading to poor spark distribution.
Other Potential Causes:
* Mass Airflow Sensor (MAF) Problems: The MAF sensor measures the amount of air entering the engine. A faulty sensor provides inaccurate readings, leading to poor fuel mixture and performance issues.
* Throttle Position Sensor (TPS) Issues: The TPS tells the computer the throttle's position. A faulty TPS can cause erratic fuel delivery.
* Vacuum Leaks: Leaks in the vacuum system can disrupt the engine's timing and fuel delivery.
* Oxygen Sensor (O2 Sensor): A malfunctioning O2 sensor provides inaccurate information to the computer about the exhaust gases, leading to poor fuel mixture.
* Transmission Problems (Automatic): While less likely to cause *only* bucking during acceleration, transmission issues can contribute, particularly if the bucking is accompanied by slipping or harsh shifting.
* Catalytic Converter: A clogged catalytic converter can restrict exhaust flow, causing power loss and rough running.
Troubleshooting Steps:
1. Start with the easy checks: Check the fuel filter, spark plugs, and spark plug wires.
2. Check for trouble codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored by the engine's computer. This can pinpoint the problem area.
3. Inspect visually: Look for any obvious signs of damage or wear to hoses, wires, and other components.
4. Test fuel pressure: If you suspect a fuel system problem, you might need a fuel pressure gauge to measure fuel pressure.
Because there are so many possibilities, a systematic approach and potentially professional diagnosis are usually required. It's best to start with the simplest and cheapest solutions first, and progress to more involved diagnostics if necessary. A qualified mechanic with experience in older vehicles will be able to efficiently diagnose and repair the problem.
