[Decker]

Recently did a road trip in hot weather(100 F in the shade) of 1500 km’s. The last leg of the journey my intake valve( that’s were the sound seems to come from) developed a loud tick/clacking sound. As well it makes a sort of chuff chuff ( best way to describe it)sound on acceleration. Also idles rough( variable revs). Could the valves/push rods need adjusting. I know they’re hydraulic and supposedly don’t need adjustment but something is definitely out of whack.
https://www.youtube.com/watch?v=96FhLJv0R-c

[ace.cafe]

I would have a look under the rocker cover.
Something sounds loose.

That kind of temperature at highway speeds or long terms is death for these engines. You are lucky it didn't come apart.

[Decker]

🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️
Found the problem, my spark plug was most of the way out. It must have loosened on the trip( this has never happened before). Gearing down on a hill it popped right out. No apparent damage and the plug threaded right back in. Whew lucky again.