Misfire driving me crazy

[04limited]

Hi all I have a 2004 gmc Sierra 1500 with the 5.3 a few weeks ago I started getting the p0304 code so I installed new plugs and wires misfire still there, swapped coils from other cylinders that showed no misfires and the problem still exists, checked intake manifold for leaks and cracks, didn't find any leaks, checked fuel pressure was about 60 psi with no leak down, checked compression all good with said cylinder reading 129 with no leak down, ran injector cleaner through the system and problem still exists and now a new code has popped up the p0332 this is driving me crazy any help will be greatly appreciated. Thanks in advance

[Chris]

304 is misfiew in cylinder 4. 332 is the rear knock sensor.

 

I had the knock sensor go out on my 04 4.8. It is probably corroded and shorted. There is a TSB for that. You should probably replace both sensors and the wiring harness for them. Then you seal them with some RTV

 

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[04limited]

I'm sorry yes I know the knock sensor condition and cure I'm more looking for help getting this cylinder 4 misfire diagnosed thanks

[aflesch]

Based on all the tests you have already run I would say a clogged fuel injector.

 

Pull the connector off of the #4 injector and get some jumper wires ready.

 

Put your fuel pressure gauge back on and turn the key on so the pump primes.

 

Use your jumper wires to actuate the #4 injector and watch for the fuel pressure to drop.

(Don't actuate it for more than 1 second at a time)

 

If the pressure does not drop the injector is bad and needs to be replaced.

[04limited]

Ok I tested the fuel injector and there was pressure drop, so I swapped the fuel injector from cylinder 4 to cylinder 2 just for piece of mind and the misfire did not follow cylinder 4 still has a misfire. Is there anything I'm over looking here? Thanks for the tips thus far.

[txab]

Check for intake gasket leaks

[04limited]

Done that a few different times

[jaredlucky16]

129 Is low need to reevaluate you leak down

 

Collapsed lifter possibly also

[8.1HD/ALLISON]

Any issues with coolant loss? Possible head gasket? What were the other cylinder compressions? Sounds like you have covered most of it. Does it miss hot? cold? any difference? What kinda of plugs and wires did you install?

[desrtrat]

check for weak/bad valve spring(s)..i agree 129 is low..