P0300

[viven44]

I didn’t but it’s getting plenty fuel from rail an pressure is rite but I’ll change that to

You might as well. Modern EFI's rely on good fuel pressure. If that is the original filter you will likely have reduced flow. Curious what fuel pressure you measured and if you measured it while the vehicle was running...

Engines misfire because
1) Timing isn't correct
2) Air or Fuel delivery isn't correct - small vacuum leaks are likely tolerated, not big ones. Fuel will definitely do it, but you've addressed everything except fuel filter
3) Plugs are gummed up and/or bad otherwise...
4) Ignition issues
5) Inadequate compression - might be good to run a compression test if fuel filter doesn't fix it

In my experience a V8 can run even on 7 cylinders well ... 6 and below will still run just OK... don't ask me how I know (shoot even 4 cylinders as we all know... more recently apparently even 2 on a DFM )... what you are experiencing appears to be a more widespread issue... my mind is at fuel still, possibly global ignition/wiring

 

[Fless]

Add to that a defective crank position sensor. Do a CASE relearn to rule it out.

If it's a Flex Fuel engine it will have an external fuel filter on the driver's side frame.

 

[Scottydoggs]

Wasn’t cats I just got them off still doing same thing

well thats just messed up.... has this truck ever sat un used for a while? mice chewing wires, or just messed up wiring could cause this. worst case the pcm went bad, or maybe its plugs got water in it and corroded the pins in the plug.

 

[03yukXL]

Mine did the exact same thing. Failed intake gasket causing a vacuum leak. While you have it out change the lifter valley gasket and if you’re really picky, the knock sensors. Worked for me (and I didn’t bother with the knock sensors)