Seat Formentor Engine Misfiring

Engine misfiring can be tricky. Rough idle, jerking, and reduced power definitely point towards a fuel or ignition problem. Since the check engine light is on, did you read the error code? It could give a clue about which cylinder is misfiring. Have you noticed any changes in fuel consumption recently? A faulty fuel pump could also cause similar symptoms, but it's less likely than a fuel injector issue. When was the last time you changed your spark plugs? It's worth checking them too. Does the rough running improve at higher RPMs, or is it consistent regardless of engine speed?

I don't have the equipment to read the error code myself. Fuel consumption seems normal. Spark plugs were changed about 30000 km ago. The rough running is present at all RPMs but seems worse at lower speeds and when the engine is cold.

Given the symptoms and mileage, a defective fuel injector is a strong possibility, especially if the rough idle is persistent across all RPMs and worse when the engine is cold. It's best to get a diagnostic scan to confirm which cylinder is misfiring and then inspect the corresponding fuel injector. Continuing to drive with engine misfiring can damage the catalytic converter. I would advise getting it checked by a qualified mechanic as soon as possible.

Thanks. The workshop confirmed a faulty fuel injector. Replaced it, and the engine runs smoothly now. Total cost was 515€.