1. Oxygen Sensor: A faulty oxygen sensor can cause the air-fuel mixture to be incorrect, leading to rough running and reduced fuel efficiency.
2. Catalytic Converter: A clogged or damaged catalytic converter can restrict exhaust flow and cause the engine to run poorly.
3. Mass Air Flow Sensor: A faulty mass air flow sensor can provide incorrect information to the engine's computer, resulting in an incorrect air-fuel mixture and poor performance.
4. Spark Plugs: Worn-out or fouled spark plugs can cause misfires and rough running.
5. Fuel Filter: A clogged fuel filter can restrict fuel flow to the engine, causing lean running and hesitation.
6. Ignition Coils: Faulty ignition coils can prevent the spark plugs from firing properly, causing misfires and rough running.
7. Vacuum Leaks: Leaks in the vacuum system can cause the air-fuel mixture to be incorrect, leading to poor performance.
8. EGR Valve: A faulty EGR (exhaust gas recirculation) valve can cause rough idling and reduced performance.
These are just a few of the possible causes. To diagnose the exact issue, it's recommended to have a qualified mechanic inspect and scan the vehicle's computer for trouble codes. The trouble codes can provide more specific information about the cause of the check engine light and poor running condition.
