2000 Suburban P0300 Misfire Code

[ct9901]

I have a 2000 Suburban 4wd that has a p0300 code. The misfires are coming mainly from #2 and #7 cylinders. Misfires only occur at idle. over 1500 rpm the misfires disappear. I have put new A/C Iridium plugs in, new wires, and new coil packs on both cylinders but the problem is not any better. All 8 fuel injectors all go to 55 psi when activated and drop to 28 when released. All tests were done with my Snap-On Solus. Driving me crazy.....Any ideas????

[autojoe]

what are your fuel trims at idle and under load?STFT LTFT.vacuum leak?

[j cAT]

Originally Posted by ct9901

I have a 2000 Suburban 4wd that has a p0300 code. The misfires are coming mainly from #2 and #7 cylinders. Misfires only occur at idle. over 1500 rpm the misfires disappear. I have put new A/C Iridium plugs in, new wires, and new coil packs on both cylinders but the problem is not any better. All 8 fuel injectors all go to 55 psi when activated and drop to 28 when released. All tests were done with my Snap-On Solus. Driving me crazy.....Any ideas????

fuel pressure is 53-62psi. ... key on engine off you should see around 60 psi. engine on it will drop to about 55psi.

shutdown engine and the fuel pressure should hold to a few psi of the operating pressure for several minutes...

if pressures are low fuel filter,pump,leaking injectors or a leaky regulator.

low fuel pressures are the most common cause of the p0300 with this engine.