Your symptoms point more towards issues related to idle speed control and/or air/fuel mixture at low RPMs. Here are some more likely suspects:
* Idle Air Control (IAC) Valve: This valve regulates airflow at idle. A dirty or malfunctioning IAC valve can lead to rough idling and stalling when the engine speed drops.
* Throttle Position Sensor (TPS): This sensor tells the engine control module (ECM) the throttle position. A faulty TPS can cause incorrect fuel delivery at idle and low RPMs.
* Mass Airflow Sensor (MAF) Sensor: Measures the amount of air entering the engine. A dirty or faulty MAF sensor can result in a lean fuel mixture at idle, leading to rough running and stalling.
* Vacuum Leaks: Small vacuum leaks can disrupt the proper air/fuel mixture, particularly at idle. These leaks are often hard to find.
* Spark Plugs and Wires: Worn spark plugs or faulty ignition wires can cause misfires, especially noticeable at idle.
* Computer Issues: While less likely, a problem with the PCM (Powertrain Control Module) or its programming could be causing the issue.
Before replacing the fuel pump (which is a more involved job):
1. Check the easy things first: Inspect the spark plugs and wires. Clean the IAC valve (if accessible). Check for any obvious vacuum leaks visually inspecting all hoses and connections.
2. Diagnostic Scan: Take your car to an auto parts store (like AutoZone, Advance Auto, etc.) and have them perform a free OBD-II scan. This will check for any diagnostic trouble codes (DTCs) stored in the car's computer. These codes can help pinpoint the problem.
3. Professional Diagnosis: If the scan doesn't reveal anything obvious, or if you're uncomfortable working on your car, take it to a mechanic for a proper diagnosis. They have the tools and expertise to identify the problem more accurately.
Replacing the fuel pump should be considered a last resort after other more probable causes have been eliminated. It's a relatively expensive and time-consuming repair.
