Boxer engine stalls at idle

I had a similar issue with my Boxer. The symptoms sound very familiar. Does it also struggle to maintain a steady idle speed? I remember my mechanic mentioning something about the intake being contaminated. Have you checked the throttle body for excessive carbon buildup?

Yes, the idle speed fluctuates quite a bit before it eventually stalls. Where exactly should I be looking for this carbon buildup on the throttle body? And is it something I could clean myself, or is it better left to a professional?

The buildup would be around the throttle plate inside the throttle body. You could try cleaning it yourself with throttle body cleaner and a soft brush, but be careful not to damage any sensors. In my case, the contamination was pretty bad, and I ended up taking it to a workshop. They did a thorough cleaning and reset the idle settings, which fixed the problem. It might be worth considering if you're not comfortable doing it yourself.

I think I'll take your advice and bring it to a workshop. I've heard the same thing about the intake being contaminated on these engines. Just got the car back. They confirmed it was the idle air control valve and that the intake was heavily contaminated. Cleaning and replacing the valve set me back 425€, but the car runs like new again!