The oil present in the chamber reduces the octane of the fuel, and can cause knock. So, your leaky valve may well have been the problem.

 

wait. you hear knock or detonation??

 

Good point! Hopefully, it will be the end of a very strange issue, fingers crossed. I replaced the leaky guide & I'll test it within the next couple days.

Yes Kaj, knock = detonation, I usually manage to hear it without det cans at 7+ counts. But this Evo was an expectation as knock was real loud, almost like a Subaru

 

oooooh! when i hear "i'm hearing knock" i think rod knock LOL. you are hearing detonation and it's setting off the knock sensor. i gotcha!



good luck with the oil idea. i hope it works!