* Dirty or Faulty Idle Air Control (IAC) Valve: This valve regulates the amount of air entering the engine at idle. A dirty valve can cause erratic idling, stalling, or rough running. A faulty valve needs replacement.
* Vacuum Leaks: Cracks or holes in vacuum hoses can disrupt the engine's air/fuel mixture, leading to poor idling. Inspect all vacuum lines for damage.
* Dirty or Faulty Throttle Position Sensor (TPS): The TPS tells the computer the throttle's position. A dirty or malfunctioning sensor can cause inaccurate readings, affecting the idle. Cleaning it might help; otherwise, replacement is necessary.
* Clogged Fuel Injectors: Clogged injectors prevent the proper delivery of fuel, resulting in a rough idle or stalling. Cleaning or replacing the injectors is often the solution.
* Mass Airflow Sensor (MAF) Issues: The MAF sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can cause incorrect air/fuel mixture calculations, resulting in poor idling. Cleaning (if possible) or replacement may be needed.
* Failing Engine Control Module (ECM): Though less common, a failing ECM can cause various engine problems, including idle issues. Diagnosing this requires specialized equipment.
* Ignition System Problems: Worn spark plugs, faulty ignition wires, or a failing distributor (if equipped) can affect combustion and lead to rough idling.
* Low Compression: If one or more cylinders have low compression, the engine won't run smoothly. This requires a compression test to diagnose.
* PCV Valve: A clogged Positive Crankcase Ventilation (PCV) valve can build up pressure in the crankcase, affecting the engine's operation and leading to rough idling.
In short: It's impossible to pinpoint the exact cause without a proper inspection. Start by checking the easy-to-access items like vacuum lines and the air filter. If you're not mechanically inclined, it's best to take your Buick to a qualified mechanic for diagnosis and repair.
