Vehicles using M120 engine list:

Engine M120

Symptoms:
- Rough idling and misfires
- Oil leaks around valve covers and timing chain covers
- Excessive oil consumption
- Overheating issues
- Loss of power or hesitation during acceleration
- Check engine light illumination

Diagnosis:
- Inspect valve cover gaskets and timing chain cover for oil leaks
- Perform compression test to check cylinder health
- Check ignition system components (spark plugs, coils, wires) for wear or damage
- Inspect cooling system for leaks, radiator condition, and thermostat operation
- Scan engine control unit (ECU) for stored fault codes related to misfires or sensor failures
- Examine timing chains and tensioners for wear or slack

Fixes:
- Replace valve cover gaskets and timing chain cover seals to stop oil leaks
- Renew spark plugs, ignition coils, and wires as needed to resolve misfires
- Repair or replace faulty sensors detected by ECU scan (e.g., camshaft or crankshaft position sensors)
- Service cooling system: flush radiator, replace thermostat, and repair leaks to prevent overheating
- Replace timing chains and tensioners if worn to maintain proper valve timing and prevent engine damage
- Address oil consumption by checking piston rings and valve stem seals; rebuild engine if severe

Prevention:
- Regularly change engine oil and use manufacturer-recommended oil grades to maintain lubrication and reduce wear
- Perform scheduled maintenance on ignition and cooling systems to avoid failures
- Monitor for early signs of oil leaks and address promptly to prevent engine damage
- Avoid prolonged high RPM driving to reduce stress on timing chains and engine components
- Use quality replacement parts during repairs to ensure longevity and reliability