Engine-Related Issues:
* Spark Plugs & Wires: Worn or fouled spark plugs can cause misfires, leading to rough running and the check engine light.
* Fuel System:
* Fuel Filter: A clogged fuel filter restricts fuel flow, causing poor performance and rough running.
* Fuel Pump: A failing fuel pump can't provide enough fuel pressure, resulting in a lack of power and rough running.
* Fuel Injectors: Clogged or faulty injectors can cause uneven fuel delivery, leading to misfires and rough running.
* Ignition System:
* Ignition Coil: A failing ignition coil can't provide enough spark to ignite the fuel mixture, leading to misfires.
* Distributor Cap & Rotor: Worn or cracked components can cause a weak spark or misfire.
* Sensors:
* Oxygen Sensor: A faulty oxygen sensor can provide inaccurate readings, leading to a rich or lean fuel mixture and rough running.
* Mass Airflow Sensor: A dirty or faulty mass airflow sensor can provide incorrect air flow readings, causing the engine to run poorly.
* Engine Management System:
* Engine Control Module (ECM): A malfunctioning ECM can lead to various issues, including rough running and check engine light.
Other Potential Issues:
* Vacuum Leaks: Leaks in the vacuum system can disrupt engine operation and cause rough running.
* Exhaust System: A restricted exhaust system can hinder engine performance and lead to rough running.
* Air Intake: A clogged air filter or obstruction in the air intake can restrict airflow and cause rough running.
Troubleshooting Steps:
1. Read the Check Engine Light Codes: Use an OBD-II scanner to read the stored trouble codes. This will give you a starting point for diagnosis.
2. Inspect Spark Plugs and Wires: Check for wear, fouling, or damage.
3. Check Fuel System: Inspect the fuel filter, fuel pump, and fuel injectors for issues.
4. Examine the Ignition System: Check the ignition coil, distributor cap, and rotor for signs of wear or damage.
5. Inspect Sensors: Test the oxygen sensor, mass airflow sensor, and other relevant sensors.
6. Look for Vacuum Leaks: Carefully inspect the vacuum lines for any cracks or leaks.
7. Check Exhaust System: Make sure the exhaust system is clear and free of obstructions.
8. Inspect Air Intake: Verify the air filter is clean and there are no obstructions in the air intake.
Professional Diagnosis:
If you're unable to diagnose the issue yourself, it's best to take your Land Rover Discovery to a qualified mechanic for professional diagnosis and repair. They have the tools and expertise to accurately identify and fix the problem.
