Fuel Delivery System:
* Fuel Pump: A weak or failing fuel pump can't deliver sufficient fuel pressure, especially at higher demands (acceleration). This is a common cause of the described symptoms.
* Fuel Filter: A clogged fuel filter restricts fuel flow, mimicking a weak pump. These are relatively inexpensive and easy to replace, making them a good starting point for investigation.
* Fuel Injectors: Clogged or malfunctioning fuel injectors might not be spraying fuel properly, leading to a rough idle and poor acceleration. Testing injector flow is necessary to diagnose this.
* Fuel Pressure Regulator: A faulty regulator might not maintain the correct fuel pressure, causing inconsistencies in fuel delivery.
Ignition System:
* Spark Plugs & Wires: Worn or fouled spark plugs prevent efficient combustion, resulting in sputtering and poor performance. Worn spark plug wires can also lead to misfires.
* Ignition Coil(s): A failing ignition coil can cause misfires in one or more cylinders, leading to rough running and poor acceleration.
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational speed. A faulty CKP can cause erratic timing and poor running.
* Cam Position Sensor (CMP): Similar to the CKP, a bad CMP sensor will disrupt engine timing.
Air Intake System:
* Mass Airflow Sensor (MAF): A dirty or faulty MAF sensor provides inaccurate air readings to the engine computer, leading to a lean fuel mixture (not enough fuel for the air) and poor running. Cleaning it might help.
* Air Filter: A severely clogged air filter restricts airflow, causing the engine to run lean.
Other Possibilities:
* Throttle Position Sensor (TPS): This sensor tells the computer the throttle position. A faulty TPS can cause erratic idle and poor response.
* Vacuum Leaks: Leaks in the intake manifold or vacuum lines can disrupt engine timing and fuel delivery.
* EGR Valve: A stuck-open EGR valve can cause a lean condition and poor running.
Troubleshooting Steps:
1. Check the easy things first: Replace the air filter and check the fuel filter. These are inexpensive and can often solve the problem.
2. Check fuel pressure: This requires a fuel pressure gauge and is the best way to determine if the fuel pump or regulator is at fault.
3. Inspect spark plugs and wires: Look for signs of wear, fouling, or damage.
4. Scan the OBD-II codes: A scan tool will read any diagnostic trouble codes (DTCs) stored by the engine computer, pointing towards specific issues.
5. Listen for unusual noises: A whirring or clicking sound from the fuel pump area might indicate a problem.
It's difficult to pinpoint the exact cause without a proper inspection. Starting with the easiest and cheapest checks (air filter, fuel filter, visual inspection of spark plugs and wires) and then progressing to more involved diagnostics (fuel pressure test, OBD-II scan) is the recommended approach. If you're not comfortable working on cars yourself, taking it to a mechanic is advisable.
