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p0300 2000 chevy 5.3

1163 Views 25 Replies 9 Participants Last post by  popsg
have a 2000 Silverado with a 5.3 and have a p0300. cylinders 1 & 8 are dead misfires at idle but when you get the rpms up the misfire moves and starts jumping around to all cylinders. have new plug wires and plugs have also had the injectors test and cleaned. tested wires from ecm to each injectors wire and they are good. have swap coils from cylinders. 1&8 are still dead till you get high in rpms then it moves to multiple cylinders. did a crankshaft and camshaft sensors and timing gear and chain. and i still have the dead cylinders on 1&8 till i get high in rpms then it moves to other cylinders and did a compression test on the motor have 150psi across all cylinders. pretty stumped any info or recommendations would be extremely helpful tired of throwing parts at it and nothing working.
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have 49psi at idle and it drops to 45-47 psi on throttle. also bleeds the pressure off when i turn truck off
did fuel pump and fuel filter and fuel pressure regulator. have 50 psi at rail. it bleeds off to 0psi when motor is shut off. what else could be the reason for low fuel pressure. injectors leaking by?
fuel pump was done yesterday along with filter and regulator. did a new tru-grade fuel pump. and I don't smell raw fuel and I checked under the truck by filter and there is no fuel leaking out. could it be leaking air from fittings and its not leaking fuel? because everything is dry. fuel pump connecter was good tested it before I install pump and made sure I had good connections. injectors were taken out cleaned and tested but were not pressure tested. as soon as i turn the truck off it bleeds to 10psi within 5-10 sec of truck being off.
the misfire is 1&8 cylinders when I have it in park at idle but when I'm in drive and cruising down the road i have no misfires at all. when stop at a red light 1&8 when start to misfire.
someone mention it could be injectors leaking down after truck is shut off
will try that next but nope only a P0300
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no vacuum leak and used ac Delco plugs
1 - 8 of 26 Posts