Help Please! 5.3L SES Light Flashing Bad Pinging

[shawnanthony]

Alright, so I need some help please! I have a 2002 GMC sierra 1500 ecsb 4x4 with the 5.3L. It has a K and N intake, Poweraid throttle body spacer, It's straight piped with cats, and it is also nelson tuned. It has a major problem that I cannot figure out. I was driving down the road and went to pass a car and all of a sudden my Service Engine Light started flashing and I lost my top end and it has a bad ping in it at over 3700 rpm. I hooked it up to a scanner it has a random misfire code p0300. Cylinder 2 has the most misfires at over 570 misfires and the rest have either 2-8 misfires on the misfire history. I have done plugs (AC Delco Iridium Gapped to .40), I have done wires (AC Delco), I have done a fuel filter, and I did a de-carbonizing test. I have done an injector balance test and all the injectors went from 52psi to 42psi. All being the exact same. I have good fuel pressure at 56psi and does not drop. I am not losing coolant either. I have always ran 93 in the truck. I through some Lucas Fuel System Cleaner through it but that did not help. I am running out of ideas. Can someone help please? Thank You, Shawn Anthony

[country_3030]

Try swapping the coil from #2 with one of the other cylinders and see if the miss fire moves with the coil.

[RedHeartbeat]

get it scanned and see the condition of the 02 sensors, they should cycle from around 100 to 900 oscillating once the engine is warm. Also, clean the MAF if you haven't done that yet, use only cleaner made for MAF sensors.

[shawnanthony]

country, we switched the coil from 2 to 4 already and that made no change. Thanks though. I just scanned it again and it through the p0300 random misfire and p0131 code O2 sensor on bank 1.

[shawnanthony]

Problem solved hopefully. Did a smoke test, no intake or vacuum leaks. Had the right person take it for a test drive and he decided that it was a cat. Drilled a small hole in front of the passenger side cat and it took it for a drive. Made a 100% turn around. So we are doing some temporary catless exhaust action. Can't Wait. Thanks for all the help though!