Hey Scotty!! You are by far my favorite you-tuber.

I have a 2011 Suburban 1500 Automatic with 270K+ miles .  One really cold day (15 degrees - that's cold for east texas 😀 ) , starting making a tapping sound (Video). Sounds like it is coming from around the Cylinder 1 area (more on that later).  Frequency increases with RPMs.   The sounds never goes away, even after it warms up. (the cold day is probably coincidence, but who knows.)

I checked oil it was fine, but did an oil change anyway, thinking viscosity of oil was wrong or something, no luck. 

Then the check engine light started coming on - misfire in Cylinder 1 - and would stutter occasionally when accelerating (that would trigger the light). If you drove it carefully, it wouldn't stutter or trigger light.  Checked ignition coils, seemed to be fine.  Changed spark plug in Cyl 1 - it was old, but not gunked up or anything, but looking, you could tell it was time to replace.  No luck - still tapping

Finally took to mechanic and he said it is something down in the engine, think maybe lifters? (language barrier made it a little difficult to understand). A buddy of mine agreed that's a good possibility.  The mechanic suggested replacing oil with half a gallon of diesel and run for a little bit in hopes of cleaning out something that might be causing something to stick.  Tried that - no luck

Sooo.. while trying to decide if I would spend several thousands of dollars replacing part of the engine, I was still driving short distances.  One day, I made it about a half a mile, when the oil pressure gauge maxed out.  Said my prayers and turned around and drove it back to the house.  Oil pressure is now constantly showing Max.  Not sure if it is related to tapping noise, or the diesel experiment, or something completely unrelated.

My question - should i just sell it to the auction yard and get my 1200 bucks?  Or is there any chance it can be fixed without pouring $5000+ into an old vehicle.  Any tips?

Thanks!!