99 Silverado Z71 P0300

[MurphysLaw88GT]

My dad's Chevy is having some miss-firing issues.It is hard to start, when it does it has a definite miss down low. The more throttle that is applied the miss is less apparent.It feels like it is down 1 or 2 cylinders at idle. He stopped by Auto Zone and had them scan it. It had P0300 listed. It has newer plugs/wires. Has anyone had similar problems?

[outlawgibbs]

if you have new plugs and wires already check your fuel system. It could be in the injectors or as simple as a fuel filter. Check your fuel pressure to make sure its consistent.

[Sprayaway Fox]

Is it a 5.7 or a LS motor? Mines a 99 with a 5.7. Just askin

[brotherbenn83]

If it is the new body style with a 4.8/5.3/6.0 check the fuel pressure regulator for leaking into the vacuum hose on it. If it was a DEAD miss, I would lean more towards an injector issue...but since it clears up as you raise RPM I doubt that is the case. The new body style truck are also notorious to have mice chewing wires underneath the underhood fuse block, but that again would probably be a dead miss. Otherwise maybe you have a sticking valve, or leaking valve seat. Try running a quart of ATF in the oil and take it out for a beating.

[MurphysLaw88GT]

5.3L engine.

[brotherbenn83]

see above post, get back to us with results. The fuel prssure regulator is on the d/s of the fuel rail and looks like this:

[MurphysLaw88GT]

It had fuel in vacuum line. Replaced regulator. Problem solved, Thanks.

[lilws6]

yet anouther gm with a regulator issue. my gf's gp has has troubles starting now and again and seems the regulator is on the pump expensive

[MurphysLaw88GT]

At least the regulator replacement on my Dad's truck seemed like it took all of 5 minutes or less...