1. Oxygen Sensor: A faulty oxygen sensor can provide incorrect air-fuel mixture information to the engine computer, causing rough idling and triggering the Check Engine Light.
2. Idle Air Control Valve (IACV): The IACV regulates the air that bypasses the throttle plate to maintain the desired idle speed. A malfunctioning IACV can lead to rough idling and Check Engine Light.
3. Vacuum Leaks: Vacuum leaks can introduce unmetered air into the engine, affecting the air-fuel mixture and causing rough idling. Check for any loose or cracked hoses or vacuum lines.
4. Fuel Filter: A clogged or dirty fuel filter can restrict fuel flow to the engine, resulting in rough idling and a possible Check Engine Light.
5. Spark Plugs and Ignition System: Worn-out or faulty spark plugs, spark plug wires, or a distributor cap and rotor (if applicable) can lead to misfires, causing rough idling and illuminating the Check Engine Light.
6. EGR Valve: The Exhaust Gas Recirculation (EGR) valve helps control emissions. If it fails or becomes clogged, it can cause rough idling and set off the Check Engine Light.
To determine the exact cause, it's recommended to have the vehicle's diagnostic trouble codes read using an OBD-II scanner. The codes will provide more specific information about the problem. Once the root cause is identified, appropriate repairs can be performed to address the rough idle and Check Engine Light issue.
