1. Spark Plugs: Make sure the spark plugs are properly gapped and installed. Check the condition of the spark plug wires as well.
2. Ignition Coil: The ignition coil may be faulty, leading to weak or inconsistent spark.
3. Distributor Cap and Rotor: Check the distributor cap and rotor for cracks or excessive wear. Replace them if necessary.
4. Fuel Filter: A clogged fuel filter can restrict fuel flow to the engine, causing it to run lean and rough.
5. Oxygen Sensor: A faulty oxygen sensor can provide incorrect feedback to the engine's computer, affecting the air-fuel mixture and causing rough running.
6. Idle Air Control Valve (IACV): The IACV controls the amount of air that bypasses the throttle plate when the engine is idling. A faulty IACV can cause unstable idling and rough running.
7. Vacuum Leaks: Check for any vacuum leaks that may be causing a lean air-fuel mixture and rough running.
8. Fuel Pressure: Check the fuel pressure to ensure that the fuel pump is delivering the correct amount of fuel to the engine.
9. Compression Test: Perform a compression test to check the condition of the engine's cylinders and piston rings. Low compression in one or more cylinders can cause rough running.
10. Computer (ECM): In some cases, a problem with the engine's computer (ECM) can affect its ability to properly control the fuel injection and ignition timing, leading to rough running.
Remember that diagnosing and fixing a rough running engine can be complex, and it's recommended to consult with a qualified mechanic if you are unable to identify and resolve the issue yourself.
