* Oxygen Sensor (O2 Sensor): These sensors monitor the air/fuel mixture. A failing O2 sensor is incredibly common and often leads to a check engine light, poor gas mileage, and rough running. A 1998 Buick likely has multiple O2 sensors.
* Mass Airflow Sensor (MAF Sensor): This sensor measures the amount of air entering the engine. A dirty or faulty MAF sensor can cause inaccurate fuel mixture calculations, leading to a check engine light, poor performance, and rough idling.
* Catalytic Converter: This component helps reduce harmful emissions. A failing catalytic converter can be expensive to replace. Symptoms might include reduced power and a rumbling noise.
* Spark Plugs and Wires: Worn-out spark plugs and ignition wires can cause misfires, leading to a check engine light.
* PCV Valve (Positive Crankcase Ventilation): This valve helps vent crankcase gases. A faulty PCV valve can cause excessive pressure buildup in the engine, affecting performance and potentially leading to a check engine light.
* Throttle Position Sensor (TPS): This sensor tells the engine control unit (ECU) the throttle position. A faulty TPS can cause poor idle, hesitation, and a check engine light.
Important Considerations for a 1998 Buick:
* Age and Wear: Parts are simply wearing out after 25+ years. Regular maintenance is crucial for preventing problems.
* Gas Cap: A loose or faulty gas cap can trigger the check engine light due to evaporative emissions issues. Check this first! It's the cheapest and easiest fix.
* OBDII Scanner: You *must* use an OBDII scanner to retrieve the diagnostic trouble codes (DTCs). These codes pinpoint the likely cause of the check engine light. Auto parts stores often offer free code reading services.
In short: Don't guess. Get the codes read. That will narrow down the possibilities significantly and save you time and money. Then, you can research the specific code to understand the likely problem and potential solutions.
