Scenic engine knocking combustion issue

Sounds rough. I had a similar issue with my Scenic, though it's an older model. Same symptoms - knocking, power loss, the works. Have you considered what fuel octane you're using? Lower octane fuel can sometimes cause pre-ignition, especially with a bit of age on the engine. Also, when was the last time you had your engine tuned? Might be worth checking the ignition timing, as that can cause similar problems.

Interesting, thanks for the reply. I've always used the recommended fuel octane, so I'm not sure that's the issue, but I'll double-check. Could you elaborate on your experience with the ignition timing? Was it significantly off, and how did you diagnose it specifically?

Well, my issue was a bit more complex, but it turned out that my car had also deposits in the combustion chamber in combination with some issues with the ignition timing, which caused erratic combustion. Best bet would be getting the engine looked at in a workshop, to be honest. Could save you a load of time and hassle trying to diagnose it yourself.

Appreciate the advice! I took it to a local garage, and you were spot on. Turns out there were excessive deposits in the combustion chamber. After cleaning and a bit of engine tuning, it's running like new. Total cost was around 425€, which is better than a full engine rebuild. Thanks again for the help!