P0300 Fault Code After Head Gasket Replacement on 1998 Chevy Silverado 1500 4x4
After replacing head gaskets on my 1998 Chevrolet Silverado 1500 4x4, I'm now experiencing a persistent P0300 fault code. The engine idles roughly and only reaches about 500 RPM. I've already replaced the head gaskets, intake manifold gaskets, fuel filter, iridium spark plugs, ignition wires, cap, rotor, distributor gear, crankshaft position sensor, and a complete remanufactured injector assembly with all injectors and regulator. Fuel pressure at key-on engine-off (KOEO) reads 60 psi, which drops to 50 psi and stabilizes after the fuel pump cycles off. I'm unsure what to do next—this issue is driving me crazy! Any insights or troubleshooting steps would be greatly appreciated.
Are there any other diagnostic trouble codes present? Do you have access to an OBD2 scanner or a code reader? You should inspect the spider assembly—this typically requires removing and replacing the upper intake manifold. PS: The fuel pressure reading appears low; double-check against manufacturer specifications to ensure accuracy.