Your noise seems to be connected to the engine revolutions it just comes in and out. What does it sound like when you increase the throttle a bit? I think that rules out HPFP, unless that's mechanical ? and rules out turbo and cats. Are you sure your scanner is reading all the codes and not just OBD ones? I find videos/recordings are often not as good as being there so you are in the best position with your stethoscope (and maybe try a piece of hose) to try to pinpoint things. The hard/slow cranking is still a consideration as well.

Im not sure why a 'knock sensor code' would enter into this conversation at all. Rod knock is not something a pre-detonation sensor would pick up. IMO

Thanks, I know internet investigations are tough.

When I touched the throttle, the tapping didn't seem to increase in frequency with rpms. The engine revved up fine even with the noise.

I'm using the NT510 to read the codes. It seems to pull everything quite well, plus there being no CEL on the dash with only the O2 code being found gives me some confidence.

It's not hard/slow starting now. It only did that when it shut off unexpectedly. Once I let it set 5-6min or so it started back up and drove fine afterwards. No codes were thrown then either other than the rich bank 1 O2 which seems odd

I can only hear the tap at the top near the head. Underneath at the block or pan, I don't hear it with the stethoscope so that's 3hy I didn't think a bearing, but who knows.

Thanks for your thoughts, all suggestions are appreciated!

Try the hose trick, sometimes that is better at giving a feel for where the sound is coming from because it's not picking up as much of the sound being transmitted through the metal or plastic.

It was shown on the video I linked; a knock fault along with a misfire fault, and a few other codes I'm not seeing.

It wasn't just about the knock fault, but I guess I could have worded it better.

Got it. :thumbup: