DS4 Boost Pressure Fault

That sounds frustrating. I had a somewhat similar problem with my 2008 Volvo C30 a while back. It wasn't exactly the same symptoms, but it also felt like the turbo wasn't kicking in properly. Did you check the boost controller or boost solenoid? Also, is there any chance the hoses connected to the valve are cracked or loose?

Thanks for the quick response! You mentioned checking the boost solenoid. What exactly were the symptoms you experienced on your Volvo, and how did you eventually pinpoint the solenoid as the problem? I'm trying to avoid replacing parts unnecessarily, so any extra details would be a great help.

Sure, so with my Volvo, the main issue was intermittent power loss, especially under acceleration. Sometimes it would be fine, other times it felt like the turbo just wasn't there. I initially suspected a vacuum leak. It turned out that the boost solenoid was sticking. The garage confirmed it with their diagnostics, but honestly, without the proper tools, it's hard to be sure. At this point, with these kinds of symptoms, I'd probably take it to a trustworthy workshop to get it properly diagnosed.

Thanks a lot! After your helpful advice, I took my DS4 to a mechanic. They diagnosed it as a faulty vacuum switching valve, exactly as I suspected. They replaced it, and the total bill came to 140€. The car is running perfectly now, with full power restored. Really appreciate your input!