u/Distinct-Reveal-6538

Been thinking about this lately. On Otto-cycle DF engines the rough rule I go by is: too rich → knock, too lean (or pilot problem) → misfire. Usually I'd look at charge air (TC, cooler, waste gate), gas quality, gas admission valves and the pilot fuel side.

In my case, I've seen a faulty gas admission valve over-supplying gas to one cylinder, which ended up causing knock.

But I'm curious what it turned out to be on your engines. Was it something boring like a fouled air cooler, or something you'd never have guessed?

Would be good to hear actual cases, since the manuals don't really tell you which causes are the common ones.