Engine Performance problem
1996 Chevy Truck 6 cyl Two Wheel Drive Automatic
I have a 96 chevy 1500 with a 4.6 L Vortec engine, engine runs rough with lots of black smoke. I replaced the fuel pressure regulator, mass air flow sensor, map sensor and engine coolant temperature sensor and still t am getting the same results and a dtc p0300. When I replaced the regulator I thought I hit the problem on the head because I saw where fuel had around the regulator clean and shinny but I got the same results when I ran the engine again. Sometimes it will ran fine at times when the engine is warm but when it is cold and has been sitting for awhile it runs terrible. I suspect the spider assembly is at fault, what do you think?
This vehicle has had problems with the injector assembly (spider injectors) leaking and it may be the fault you have.
If you have access to a fuel pressure gauge, prime the system by turning on the ignition (vehicle not cranked), then close the isolation valve on the fuel gauge. This isolates the injectors and regulator so the gauge will only read if there is a pressure drop through one of those components.
If you don't have access to a gauge and if the upper intake plenum gasket was replaced already, it may still be reusable for an inspection. Remove the upper plenum again and then reinstall the fuel delivery lines. Have an assistant prime the system again (make sure you trust the guy so he doesn't try to start it) with the injector tips out of their holes and inspect for dripping fuel.