Seat Tarraco Hybrid Engine Running Rich

I have a similar Seat Tarraco, though I have the petrol engine. I experienced similar symptoms a while back: reduced engine power, rough running, and the check engine light illuminated. My fuel economy also took a significant hit. Have you checked your spark plugs? A faulty ignition system can sometimes cause unburnt fuel to enter the exhaust, potentially damaging the catalytic converter. Additionally, consider inspecting the intake manifold for any leaks or blockages. A leak in the intake manifold can disrupt the air fuel mixture and cause the engine to run rich. I would suggest investigating these components before assuming the fuel injectors are the culprit. Fuel injectors deliver fuel to the engine. If they are leaking or stuck open, they will deliver too much fuel, causing a rich condition.

Thank you for your quick reply! I have not checked the spark plugs or the intake manifold yet. Could you elaborate on how a problem with the spark plugs or the intake manifold can cause the engine to run rich?

Certainly. If your spark plugs are fouled or not firing correctly, they won't completely burn the fuel in the cylinders. This unburnt fuel then gets pushed into the exhaust system, making the engine run 'rich' as the oxygen sensors detect an imbalance. As for the intake manifold, if there's a leak, it can cause unmetered air to enter the engine. The engine control unit (ECU) tries to compensate by adding more fuel, again resulting in a rich condition. However, given your symptoms and mileage, a faulty fuel injector is also a strong possibility. I would still recommend having a professional diagnose it to be sure. It may be best to take it to a workshop.

I took the Tarraco to a certified workshop, and they confirmed that the fuel injectors were indeed faulty. They replaced them, and the engine is now running smoothly. The final bill was 515€, which is in line with what I expected. Thank you for your advice!