I’ve already done all the typical stuff to try and fix this problem - new spark plugs, ignition coils, fuel injectors. I know for sure there is a bad valve cover gasket, the old spark plugs had some oil on them, but I was told It’s probably not related. Any help would be appreciated, the problem is getting annoying and expensive.
Oh, also, this is some chattering in the engine while accelerating, coming probably from the side cylinder 4 is on. And in addition to the misfire code, I also get a lean fuel/air mixue code (forgot the number.)