well, if this helps, i'll explain how mines happened....
one day i was driving, oil was low, not too low, but i consider little ting under the mark low.....now i mash the pedal halfway and it reaches boost at about 0.3kg/cm3 and i hear a knock knock knock slight and i release, driving normal etc....went to my mechanic, he checked it, thought it was a bearing but was'nt constant so he tell me come morning to change oiil and add and additive named "Protech" which he thought somewhere was scorched and that should over time restore it and stop the noise....well driving normal and ting for a week now, and now over 3000rpm the knock is hearable more and more and as i rev over 2000rpm, the more higher the rpm raises the faster the knock goes....one day by mistake i just testing out the automatic transmission manually by going on L, then 2 and D....and instead of D, it went on Neutral by mistake and it rev to about 6500RPM and then the knock was constant and slight this time at 1500rpm and up....so i went by mechanic, checked it, he was'nt there, i coming home, and as i reach home, the car kinda jerking back and then all i hearing at idle and ting while on drive without mashing gas, KNOCK KNOCK KNOCK nonstop...come home, could drive it but jerking, nonstop knocking, even when i start....
they check it, and when they open up, bearing spin out.....also before, as you said, the plugs, one of my plugs was bad and giving me a miss like before any knock at 2500-3000rpm....and i did injector clean out thinking it was that...nope, still miss a bit.....then i sya i go change plugs but never get chance to....so i watching and from the radiator going back, the engine open nah, 4th piston, i watch it....i push it, and then ting drop down easy
it was that bearing and rod gone thru....
so i kinda guessing it was cause of non synthetic oil that was 1 month overdue changing and bad plug....
i get a shortblock, changing plugs one time, and checking everything, oil pressure gauge going in, etc to make sure nothing wrong again.
I did a boo boo.....The original air filter setup had an attachment for this selonoid valve that supposed to take exhaust fumes back to the engine to burn unburnt hydrocarbons. The short ram did not have any attachment for this selonoid valve.....so instead of leaving it hanging in the engine I strapped it to the air condition line. APPARENTLY this valves opens and closes thus going "tock""tock""tock""tock".
