Lexus LX Knocking Sound

I had a similar issue with my LX. Does it feel like the engine is hesitating, like a runner stumbling mid-stride? Check your knock sensor. Sometimes they go bad and cause the engine to pull timing, which could explain the reduced power and jerking. Have you tried running higher octane fuel? It might help mitigate the knocking if it's pre-ignition.

Thanks, I'll investigate the knock sensor. I've used the recommended octane. Could it be the cylinder heads, and would cleaning the combustion chamber help?

While cylinder head issues are possible, and cleaning the combustion chamber might help, my experience points towards something simpler first. I'd still lean towards the fuel/ignition side. In my case, it turned out to be excessive carbon buildup. Best to take it to a workshop; they'll be able to diagnose it properly.

I took your advice and brought the vehicle to a trusted mechanic. They confirmed deposits in the combustion chamber were causing the knocking. The total repair cost came to 425€.