Looking to buy my frinds 2002 Chevy Silverado. It has a 5.3 and getting P0300 codes. It is very hard to start, you have to cycle the key many times to get fuel for it to start. After may attemps, it will start and after a bit, idle fine. When you give it gas, it dies. If you feather with the throttle, it may rev up to 2000-2500 RPM's. It does not have enough power to drive it. Installed new fuel pump and filter. Has 55 to 60 fuel pressure. Replaced intake gaskets, plugs and wires. Plugged the computer in and cylinders 4&5 are the misfires. Swapped around coil packs, no change. Swapped injecters, no change. All cylinders have 120 psi compression. Replaced MAF sensor and IAC valve. Nothing. This all started when the truck got stuck in the mud. A little rocking back and forth and then it died. One thing the EGR tube where it goes in the plenum, was kinda burnt. Had to put a new grommet in it. Could that of caused any damage internally? I would really like some advice and thank you in advance.

Disconnecting the exhaust pipes would not affect the compression. Did you have the throttle body wide open i.e. butterflies wide open when you did the compression test? Disconnecting the exhaust pipes would not affect the compression. Did you have the throttle body wide open i.e. butterflies wide open when you did the compression test?

I disconnect the exhaust to see if the converters may of been plugged. I only cranked the engine without pressing the throttle when I checked the compession. Now looking back, that should of been opened. I was looking more for a difference between cylinders for a head gasket maybe. The truck ran fine prior to getting stuck. It was only down a few inches on an incline. It was not "hot rodded" trying to get it out. We just pulled it with a strap. My first thought was the fuel/sedement in the tank from rocking may have plugged the fuel filter. By the way, thanks for the help! I disconnect the exhaust to see if the converters may of been plugged. I only cranked the engine without pressing the throttle when I checked the compession. Now looking back, that should of been opened. I was looking more for a difference between cylinders for a head gasket maybe. The truck ran fine prior to getting stuck. It was only down a few inches on an incline. It was not "hot rodded" trying to get it out. We just pulled it with a strap. My first thought was the fuel/sedement in the tank from rocking may have plugged the fuel filter. By the way, thanks for the help!