Last night I drove home from a buddies house and specifically heard the knocking, I COULD DEFINITELY HEAR IT. Drove home carefully, did not take it over 3500 rpm's. Today I woke up and popped the hood, one of my spark plugs didn't look like it was pressed down all the way, it was connecting but the rubber from the top wasn't touching the VC, then the bad part.... I found some oil in and around it.