Citroen C8 Vacuum Switching Valve Issue

Sounds familiar. I had similar symptoms with my C8. Check engine light, power loss at higher speeds, and a definite decrease in fuel economy. It felt like something was holding the turbo back. Have you noticed any weird noises, like a whooshing or fluttering sound when accelerating?

Whooshing, yes! Especially noticeable when climbing hills. So, you're saying it's likely the same thing? How did you nail that down, and what part exactly gave you trouble? I am kinda thinking about pressure drop, compressor surge, bypass valve or boost controller but I'm just not sure if those are the problems

The whooshing sound is a good indicator. In my case, it turned out to be a faulty vacuum switching valve, which messes with the boost pressure control. The pressure drop was all over the place, resulting in turbo lag and poor performance. Honestly, diagnosing these things without the proper equipment can be a nightmare. Consider taking it to a workshop; they can pinpoint the issue quickly with diagnostics.

Thanks a bunch! Dropped it off at the shop this morning, and you nailed it – vacuum switching valve. They quoted me 140€ for the repair, not ideal but at least I know what it is! Should be back to its old self soon. Appreciate the help!