Vehicles using AEX engine list:

Engine AEX

Symptoms:
- Rough idling and poor acceleration
- Engine misfires or hesitation under load
- Increased fuel consumption
- Check Engine Light (CEL) illumination
- Difficulty starting, especially when cold

Diagnosis:
- Inspect ignition components: spark plugs, ignition coils, and leads for wear or damage
- Check for vacuum leaks around intake manifold and hoses
- Test fuel injectors for proper spray pattern and operation
- Scan ECU for fault codes related to misfires, oxygen sensors, or idle control
- Examine timing belt condition and tension, as a worn belt can cause timing issues
- Verify proper operation of the idle air control valve (IACV)

Fixes:
- Replace worn or fouled spark plugs and faulty ignition coils
- Repair or replace cracked or leaking vacuum hoses
- Clean or replace fuel injectors if clogged or malfunctioning
- Replace timing belt and tensioner at recommended intervals (typically every 60,000 to 90,000 km)
- Clean or replace the idle air control valve to restore smooth idling
- Address any ECU fault codes by repairing related sensors or wiring

Prevention:
- Follow manufacturer’s recommended maintenance schedule for timing belt and ignition components
- Use quality fuel and perform regular fuel system cleaning to prevent injector clogging
- Regularly inspect vacuum lines and intake components for leaks or damage
- Replace spark plugs at intervals specified in the owner’s manual (usually every 30,000 to 60,000 km)
- Keep the engine bay clean to avoid dirt and debris affecting sensors and valves

By adhering to these diagnostic steps and maintenance practices, owners of Seat Arosa, VW Vento, Golf III, and Polo with the AEX engine can ensure reliable performance and minimize common issues associated with this 1.4L 44kW engine.