2004 GMC Sierra 2500 HD, 227,000 miles 6.0L V8.
While driving up hills or increasing load, the CEL will flash multiple times, I pull over as I know CEL flashing is not good. I turn the truck off, allow it to sit for a few minutes, whip out the code scanner, only code that was there happens to be P0300. Truck has poor MPGS, idles rough, loss of power.
this happens every time I drive this vehicle as I use this truck to pull my trailer that weighs around 4000 lbs. Problems come and go. Some days I can drive the truck for an hour with no problems, come up to a red-light, BAM, CEL is flashing, truck is bouncing side to side due to the poor idle, other days this happens while sitting in the parking lot of my job with the ac on.
Truck has been to the shop several times as I’m no mechanic. Parts replaced are as follows:
Intake Manifold Gasket
Sensor 1 Bank 1 O2 Sensor
Sensor 1 Bank 2 O2 sensor
Any help would be appreciated, as I’m getting very frustrated…