So this is gonna be long and I will do my best to explain without confusing. So I have a 2002 Chevy Silverado 1500 5.3l vin t with 127000 miles on it. It has been randomly misfiring for 2 months now. It all started as a cylinder 2 misfire and was so random and sporadic and only really happened after the truck was one and I accelerated hard I didnt think much of it but tried to fix it anyways. Well after a couple unsuccessful attempts It eventually became a misfire on all of bank 2 and was getting consistent but it never misfire at idle so I kept working at it. Now it Misfires on cylinder 6 and 4 at idle cylinder 6 being the worst. At 1000 to 2000 rams Cylinder 4 becomes worst then 6 all the while 2 and 8 might read 1 or 2. Once you rev it up to 2500 rpms or more Cylinder 2 becomes the worst and cylinder 4 and 6 start to get a lot better and 8 stays around 1. Once you let the rams down to idle it starts idling rough and sometimes cylinder 5 will start misfiring for a cycle but then it will stop. I have literally replaced and tried everything I will list everything I replaced in the order I did it just hoping someone can tell me something I didnt think of.
Spark plugs and wires
Ohmd all the wires
Throttle body gasket
Wiring harness for injectors
The crossover fuel line in top of intake
Spark plugs and wires again (they were fouled)
Intake gasket again (overnighter it and smashed the gasket)
Checked the lifters none were sticking and moved like they should
Scoped out the pistons they were all good except minor oil residue on cylinder 6.
And i think thats it other then checking for vacuum leaks and replacing various o rings.
The truck had all new fuel lines 3 months prior went through and checked them all anyways the fuel line into the rails had a bad clip and o rings so I replaced it still nothing.
As a side note 90% of those parts were all failing or bad upon removal and yet it still misfires.
My buddy has an HPTuners so we checked everything through there very thoroughly. We are both at a complete loss. Also I know about checking the head gasket but so far the engine doesn’t overheat and no coolant has gotten into the oil so we are pretty sure thats okay. Also checked the cat and it appears to be functioning normally.
Other then that we checked endlessly for fuel leaks and vacuum leaks and have come across a few and have fixed them all but still no luck.
So any advice I can get will be highly appreciated. Also as a side note the truck doesn’t have an egr didnt have one from factory I bought it off my friends dad eho has been helping me who bought it new 18 years ago.