The truck has brand new AC Delco iridium spark plugs/wires, brand new fuel filter, clean air filter, and of course the transmission rebuild with new torque converter. For a while, I've been getting P0300 (random multiple misfire) and P1133 (heated o2 sensor bank 1 sensor one, which IIRC is the rear o2 sensor), but occasionally after these hard acceleration episodes, it would give me a P0303 (Cyl 3 misfire) code, so I tried swapping coil packs between the #3 and #5 cylinders, with no luck, so the coil packs seem to be in operation. Last night, we did do a pressure test on the fuel pump...upon turn-on, the pressure goes up to around 54-55psi, and once the truck is started and idling, the pressure drops to between 48-50psi, which I was told is normal. I've also used MAF cleaner on the MAF sensor, although I wasn't pulling codes. No luck there either.
We're at a loss with this, sort of trying to replace the fuel pump and see if that works...it has been emitting a high pitched whine for a while, but not all the time, so I'm not sure if the pump would be to blame or not. Truck is, of course, a 2001 Silverado 1500 Z71, 4x4, with the Vortec 5300 V8 motor.
I've included a link to a video I took the other night of the problem. I easily accelerate from a standstill with no problem, but around the 0:20 mark, I hit the accelerator and the rattle becomes more noticeable, and the SES light begins flashing.
Friday, February 8th, 2013 AT 4:47 PM