97 5.7 vortec random misfire

[94chevyred]

One day My truck began running rough at idle and it was throwing a p0300 code so I ended up replacing cap, rotor, plugs and wires, and Pcv valve and it didn't solve the issue. So I took the upper plenum off and there was some fuel puddling and 2 of the injectors so I decided to just upgrade to bwd mpfi, and I still get a random misfire. It has no vacuum leaks, Compression is good, egr valve is good. Timing is dead on. I did a fuel pressure test and its a 60 psi with key on and 49 psi at idle. Would that actually cause a misfire?

 

[michael hurd]

That fuel pressure is low with it running. If you have good compression, and the cap/rotor and wires have recently been done, I would look at the fuel pressure. It may be good to pull the connector on the pump wiring and verify the voltage is good. The wiring on these trucks is getting old, and can often result in problems, especially on the ground side. Poor connections will result in voltage drop.

You could also consider adding an additional ground wire to the sending unit when you have it apart.