Volvo S90 Cylinder Pressure Fluctuation

That sounds familiar. I had similar issues with my 2016 Opel Insignia – higher fuel consumption and engine light. In my instance, it was a consequential error. It turned out not to be the head gasket, timing belt, or intake manifold itself, but another sensor throwing everything off. Like a domino effect.

Interesting. Consequential error from another sensor? Can you elaborate on what the initial error was in your case?

Certainly. In my Opel, it was the oxygen sensor. It gave incorrect values to the engine control unit, which then caused the cylinder pressure issue as a knock-on effect. Considering your Volvo's symptoms, and the complexity of modern engines, I highly recommend getting a diagnostic check at a workshop. They can pinpoint the root cause.

Thanks for the advice. I took it to the workshop, and you were spot on - it was a sensor issue causing a consequential error. Repair cost was 0€ since it was covered by guarantee!