P0300 Fault Diagnosis: 2003 Chevrolet Silverado 6.0L V8 Engine
My 2003 Chevrolet Silverado with a 6.0L V8 engine is experiencing severe misfires, indicated by fault code P0300. The truck barely runs and has been through a fuel filter replacement and injector balance test. The misfire graph from the OBD-II scanner shows inconsistent combustion across all cylinders. Fuel pressure readings show an initial 55 psi that drops to 28 psi under load—this drop is affecting performance. I've confirmed adequate spark per cylinder, but the engine still struggles to maintain consistent operation. What could be causing this issue? Are there known fuel delivery or injector problems in this model year and engine configuration?
55 psi is below the typical specification for a 2003 Chevrolet Silverado 6.0L engine—what is the manufacturer's recommended fuel pressure range? Additionally, could you provide the scanner readings for fuel trim (FT) values and pre-catalyst oxygen sensor voltages? Any signs of excessive fuel in the oil might indicate a fuel system leak or injector malfunction.