Seat Ateca Diesel Engine Problems

That sounds a lot like what happened with my Seat Ateca. I have the same model, though a slightly older version. I had similar symptoms: rough idling, the engine light was on, and the fuel economy was terrible. One thing to check: When was the last time you replaced your air filter? A dirty air filter can sometimes cause issues with the mass air flow sensor, as it can affect the air-fuel ratio. Have you checked that already?

Interesting, thanks for the tip! The air filter was changed about six months ago during a service. But could a dirty air filter really cause all these problems, like the engine stalling and the smoke?

Yes, definitely. While a relatively new air filter makes it less likely, problems with the mass air flow are very common, especially with those symptoms. From my experience, and considering the mileage, it is very probable that the mass air flow sensor is defective. If you're not comfortable diagnosing it yourself, I would recommend taking it to a trusted mechanic to get it checked out. They will be able to confirm the issue and replace the sensor if needed. Trying to drive it for long in this state could cause even more damage.

Huge thanks for your help! Took it to a local garage, and they confirmed it was the mass air flow sensor. New one fitted and the car is running great again. Bill came to 365€, which I think is reasonable. Appreciate the advice!