Hello all. As my headline states, I’m at the end of my rope. I have a 2006 Chevy Avalanche 1500 Z66, 5.4 Vortec engine. It has less than 80,000 on the clock, and I have been driving it for about three years with no issues. About a month ago I was on the interstate and the thing just started losing power, no CEL or idiot lights, just wasn’t acting right. I limped on to the next exit, called AAA and had it hauled home. I did some research, and started simple: new coil packs, plug wires, plugs, cleaned the MAF, changed the air filter, no change. Drove it after I cleaned the MAF, and the CEL started flashing. I immediately pulled over and plugged in my code reader, showed me a P0300, misfire. I checked for an intake leak, couldn’t find one, but I only know how to throw parts so I ordered new gaskets. I realized I was at the end of my skill set, had it hauled to a local guy. He went over it, said it was misfiring randomly on all cylinders, tried dry gas. It improved so that it was misfiring on one bank, he said it may be injectors. Pulled injectors, soaked them in cleaner overnight, reinstalled but switched them over to opposite sides, back to misfire on all cylinders. Said it wasn’t the intake gaskets, changed his mind, installed them new and discovered they had been changed previously. No change. He said he went through the wiring, found a couple bare wires, probably fried the PCM. Ordered a new one, installed it today, no change. I talked to a mechanic who is on the fire department with me, he said upstream O2 sensor. Asked my guy, he said readings were normal on O2 sensors. Other guy asked about a fuel pressure test, he said he did one and it was normal.

If this was any other truck, I’d sell the son of a bitch. Thing is, this thing belonged to my wife’s grandfather, so it has sentimental value. We got it for a decent price as well, and it is in great shape.

The question is, what the hell is wrong with this bastard? Any help is appreciated.