XC90 Hybrid Reduced Engine Power

I had a similar issue with my XC90 – though it's an older model. Those symptoms – reduced power, smoke, rough running – point towards a problem in your exhaust gas recirculation system. Especially the hissing sound suggests a vacuum leak. Have you checked for any obvious signs of damage to the EGR valve or any of the surrounding hoses? It could be a faulty valve or perhaps just a clogged passage.

I haven't pulled the EGR valve itself yet, as I'm not sure where to start looking. Is it tricky to get to? And when you say 'vacuum leak', where specifically should I be looking? Any particular hoses or connections that are prone to failure on the XC90?

Accessing the EGR valve can be a bit tight depending on your engine configuration, but it’s usually bolted onto the intake manifold. As for the vacuum leak, closely inspect all the small vacuum hoses connected to the EGR valve and intake manifold. They tend to crack and become brittle over time, particularly near the connections. Honestly, given the symptoms you're describing, and the fact that your car is still relatively new, I'd suggest taking it to a reputable workshop. A defective EGR valve can cause increased wear on the catalytic converter and increase vehicle emissions. A professional diagnosis will save you time and potential money.

I was trying to avoid the workshop, but it sounds like that's the smartest move. I appreciate you confirming my suspicions about the EGR valve and the vacuum leak. Turns out that the EGR valve was indeed defective/jammed, and the total repair cost was 355€. I learned my lesson about ignoring the warning signs!