Mercedes Viano Diesel Engine Issue

That sounds frustrating I had a similar issue with my old Audi A4 Check for a vacuum switching valve defect The symptoms are the same: power loss, sluggish acceleration It felt like trying to run a marathon with a blocked nose That can also cause a compressor surge If the valve isn't working right, it messes with the turbo Does the engine seem to be working harder than it should?

A vacuum switching valve is new to me Where would I find that, and could I check it myself without making things worse? Also, how would I know if the engine is working harder than it should? What should I be listening or looking for?

Diving in yourself might be tricky But yes the engine will be noticeably louder when working harder In my case, the valve was tucked away near the turbo Unless you're comfortable poking around under the hood, it might be best to take it to a workshop They'll have the tools and know-how to diagnose it properly You don't want to accidentally create an even bigger vacuum leak or something

Thanks so much for the advice The vacuum switching valve was the problem The workshop confirmed it and fitted a new valve The engine's back to its old self The total cost was 140€, which I can live with Engine performance is fantastic now I appreciate the help