QuestionI have a 2002 GMC sierra 4wd pickup that is having major issues but no one knows exactly what. It misfires on three different cylinders, it wont go faster than 65 and thats with the rpm's between 4 and 5 and with the gas pedal to the floor. I replaced my fuel pump and the intake manifold gaskets HELP.
Answerhi
if the misfires are on 3 or 4 adjoining banks (eg.2,4,6,8 or 1,3,5,7) then I would suspect either a Catalytic converter OR the front oxygen sensor for that bank of cylinders.
If the misfires are on 7,8 and either 6or5, then I would suspect water in the fuel rail that collects in the rear of rail since the rail has a slightly rearward angle.
If the misfires are alose to 3,5 7 I would suspect the fuel pressure regulator leaking.
Other than these common problems, it coulod be 3 faulty injectors, injector harnesses, low compression on the 3 cylinders (bad head/head gasket) or plugs/plug wires.
Hope this in some way helps
God Bless
