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p0300 2000 chevy 5.3

1161 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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Questions from me, I know very little about FI rails. Is there a regulator to open up to send excess fuel pressure back to the gas tank? During idle, can gas be squirted into the air intake past the MAF sensor? Can a test light or voltmeter be placed at the fuel injector to know that the injectors are working at idle Or with a finger, feel the injector that it is operating?
DO NOT use a test light to check injectors. Use what is called Noid light . And will tell you if the is firing an injector .
no vacuum leak and used ac Delco plugs
An Oscilloscope could tell you . Back in the day they were called tune up machine. It tell you how much voltage to each plug along with duration,also tell whether a cylinder is rich or lean.
DO NOT use a test light to check injectors. Use what is called Noid light . And will tell you if the is firing an injector .
ARES 71500 - Noid Light & IAC Test Kit - Easily Eliminate EFI and IAC Systems as Causes for Non-Starting Vehicles

This is the one I bought to work on the same vehicle type. Worked well.
I already suggested that but I guess not everybody has access and know how to use and interpret signal value and synch.

You will need to find a way to scope the crankshaft position sensor as well as the ignition and fuel injector signals on this misfire condition. Anything else is guesswork.
If your motor is starving for air might cause this. Air filter, throttle body not opening enough, blockage in the air intake system. Just thinking aloud.
Welcome to my world! I’ve been fighting P0301/P0300 on my 2007 (classic) 5.3 for months. Same engine as the 1999-2006 Silverado.
My engine light came on the morning of 1/17 when I started the engine. So I, being cautious, shut it down and had it towed to a mechanic in town. They told me it was misfiring on #1 and #8 and needed new plugs/wires. Cool!!! I replaced with OEM plugs and wires. (~$200) Started up. No change to the results.
Took it to a dealer who checked it over and assessed “something is wrong inside the motor”. (DUH!)
They quoted me $8K+ to rebuild or $9800 to replace the motor.
I decided if it’s that bad, I would see if I could find the issue(s). Worst case, I’m replacing the motor. (Not at the dealership price)
I replaced the MAF and it got a little better. Now, I’m only getting P0301 AND P0134.
Replaced fuel injector #1. No change
Replaced ignition coil #1. No change.
(One at a time) swapped - plug, wire, coil, injector - #1 and #2 - still P0301/134
Replaced intake manifold gasket. Still P0301/134.
Replaced Oxygen sensor Bank01. Still getting P0301 and an occasional P0134.
Replaced valve cover since my valve cover is the one with the PCV valve built in to the valve cover. Still P0301!
Ran top engine cleaner through it…BETTER! But P0301 came back up.
Now, I am convinced I have a camshaft/lifter issue with my motor. I guess the dealership was right? Given the cost of having this done, I am researching the best place to have the engine replaced. I have no confidence trying to replace the camshaft and lifters on my own.

FYI in my research I came across this GM Service bulletin, which is why I ran the too engine cleaner.

You might want to check if this might be the cause of your issue.
Before you end up being a Platinum member of the local Auto Parts Store like me. :)

Best of luck!!!

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