Vehicles using M166.990 engine list:

Engine M166.990

Symptoms:
- Rough idling and stalling
- Loss of power or poor acceleration
- Engine misfires or hesitation
- Check Engine Light (CEL) illumination
- Increased fuel consumption
- Unusual engine noises or vibrations

Diagnosis:
- Inspect ignition components (spark plugs, ignition coils) for wear or damage
- Check for vacuum leaks around intake manifold and hoses
- Scan for fault codes using an OBD-II scanner to identify sensor issues (e.g., MAF, oxygen sensors)
- Test fuel injectors for clogging or malfunction
- Examine the timing chain and tensioner for wear or slack
- Inspect the crankshaft position sensor and camshaft position sensor for proper operation

Fixes:
- Replace worn or fouled spark plugs and faulty ignition coils
- Repair or replace cracked or leaking vacuum hoses and intake gaskets
- Clean or replace the mass airflow (MAF) sensor and oxygen sensors as needed
- Service or replace clogged fuel injectors
- Replace timing chain and tensioner if excessive wear or noise is detected
- Replace faulty crankshaft or camshaft position sensors
- Perform routine oil changes with recommended oil to maintain engine lubrication and timing chain health

Prevention:
- Follow the manufacturer’s recommended maintenance schedule strictly, including timely oil and filter changes
- Use high-quality fuel and spark plugs to reduce deposits and misfires
- Regularly inspect vacuum lines and intake components for leaks or damage
- Avoid prolonged idling and aggressive driving to reduce engine stress
- Monitor engine performance and address warning lights promptly to prevent further damage
- Keep the engine bay clean to prevent dirt and debris from affecting sensors and components

By adhering to these diagnostic steps, fixes, and preventive measures, owners of vehicles with the M166.990 engine can maintain reliable performance and avoid common issues associated with this powerplant.