Citroen C3 engine stalling after fuel filter change

Sounds like a faulty fuel pressure regulator. Did you perhaps introduce any air into the fuel lines when you changed the fuel filter? That can sometimes cause issues with the regulator and trigger those symptoms. Rough idle, engine misfire and reduced fuel efficiency can all be related to the regulator. I would check error entries first.

Air in the fuel lines, huh? That's a good point, I probably messed something up there. But could that really damage the regulator itself? And how would I even check for those 'error entries' you mentioned? Sorry for the newbie questions!

Air in the fuel lines shouldn't damage the regulator directly, but it can cause it to malfunction temporarily and potentially lead to a stored error code. By error entries I mean the error codes, you need an OBD2 reader to check those. Given the symptoms and the timing with the filter change, it's highly likely the fuel pressure regulator is the culprit. Since the car is old I would consider taking it to a workshop. Fuel regulators are not that expensive.

Thanks a bunch for the help! I took it to a local mechanic, and you were spot on – it was the fuel pressure regulator! The error log pointed to it too. They replaced it, and the car is running perfectly again. The whole thing cost me about 45€, which isn't too bad. Really appreciate you pointing me in the right direction!