Vehicles using AQM engine list:

Engine AQM

Symptoms:
- Reduced engine power and sluggish acceleration
- Difficulty starting the engine, especially in cold conditions
- Excessive smoke from the exhaust, typically white or grey
- Increased fuel consumption and rough idling
- Engine warning light illumination

Diagnosis:
- Check for clogged fuel injectors or fuel filter restricting fuel flow
- Inspect the glow plugs for proper operation, as faulty glow plugs affect cold starts
- Examine the EGR valve for carbon buildup causing poor combustion
- Test the intake manifold and turbocharger (if applicable) for leaks or blockages
- Verify timing belt condition and tension, as incorrect timing affects performance

Fixes:
- Clean or replace fuel injectors and fuel filter to restore proper fuel delivery
- Replace faulty glow plugs to improve cold start reliability
- Clean or replace the EGR valve to prevent exhaust gas recirculation issues
- Repair any intake or turbocharger leaks and clean air intake components
- Replace the timing belt if worn or damaged, ensuring correct timing settings
- Regular oil changes with recommended grade to maintain engine health

Prevention:
- Use high-quality diesel fuel and regularly replace the fuel filter every 20,000–30,000 km
- Perform routine maintenance on glow plugs and EGR system to avoid buildup and failures
- Change engine oil and oil filter at recommended intervals to prevent internal wear
- Monitor and maintain the timing belt according to manufacturer schedule (usually every 60,000–90,000 km)
- Avoid prolonged idling and ensure the engine reaches operating temperature during drives to reduce deposits

By adhering to these diagnostic steps, fixes, and preventive measures, owners of vehicles equipped with the AQM engine code—such as the Seat Ibiza, Cordoba, León, Skoda Octavia I, and VW Polo—can maintain reliable engine performance and longevity.