P0300 Intermittent problem for 3 Years

Question

Hi, I have  2004 GMC Yukon Denali XL 6.0L it has a P0300 code.
Me and my father have been chasing this problem for over 3 years... We have replaced multiple components. We have changed spark plugs, spark plug wires, 8 coil packs , intake gasket, fuel filter , 8 fuel injectors, Knock sensor 1,2 (TSB), Knock Harness, Map/ Maf sensors, Throttle body, coolant sensor, Battery, Flashed ECU, Replaced the ECU.
We have did many tests and we still have a P0300 code. If you have any ideas or new tests this will help alot!!!!
Thank you

Answer 1

P0300 Random misfire

A ignition analyzer would be the diagnostic tool or a scan tool that can read cylinder contribution. When it comes to a P0300 what usually gets missed it the fuel pressure regulator that intermittently seeps fuel into its vacuum connection that one area that should be checked, another is exhaust back pressure. you can clear the code loosen the exhaust connection near the catalytic convertor and duplicate when a P0300 occurred.