P0300 Chevrolet -

Question

Brand new 5.3L long block installed on a 03 Silverado.
Injectors plugs and wires off old motor were in good shape but
now is throwing p0300 code.
Changed fuel filter and cleaned MAF sensor but still giving the code.
ANY SUGGESTIONS?

Answer 1

Hi there,

Since you did the change over, I would look for intake manifold gasket leaks as a possible cause, or possibly vacuum lines either disconnected or installed wrong to some of the solenoids. This can cause vacuum leaks and multiple misfires.