Misfire of # 4 Cylinder P0304 code - Misfire happens intermittently, at idle and or driving.

[2014 Z51]

I'm New here. I've been chasing this same issue (Misfire of # 4 Cylinder P0304 code) for a couple of years now. I have changed the plugs, plug wires, coil pack (twice) fuel injector (twice). MAF Sensor, Cam Sensor, and the ECU, and I checked the compression, and it good. This Misfire happens intermittently, at idle and or driving.

I'm so frustrated, I've never had and issue like this, that I couldn't fix.

Any advice would be Greatly appreciated.

 

[RonD]

1996 3.0l would be Waste Spark so both cylinders 3 and 4 would not fire if it was a Computer or Coil pack issue
But reverse 3 and 4 spark plug wires on the coil pack to be sure its not the coil

"new" just means NEVER EVER tested, so grain of salt on any untested(new) parts

If you have an old time timing light you can put it on #4 wire and see if idle miss is caused by no spark on #4 wire
And don't take the Cam sensor(misfire detector) and computer as "the word of God" on #4 being the cylinder that is misfiring, its just not that accurate
The fact you FEEL a misfire means there is one, but choice is 1 to 6 not limited to #4

By far the most common cause of a misfire AFTER bad spark plug, is a compression issue, exhaust valves run hot and WILL get burnt and leak, that's why every person who's even slightly interested in DIY engine work has heard of "a valve job", it fixes burnt exhaust valves which is the most common mechanical failure on all engines with exhaust valves
If this problem was slowly getting worse and worse then that's the most likely issue, compression

The 3 things that allow a cylinder to fire are
1. spark, at the right time
2. fuel, with air mixed in
3. compression

If you eliminated 1 and 2 as the possible problem, then you are left with #3

Long shot but not a no shot is leaking intake valve guide seals, oil gets sucked in(vacuum in intake) and collects on the back side on intake valve, and is then sucked into cylinder with the air/fuel mix, if there is enough oil then partial or full misfire
Spark plugs tips will tell that tale, darker blackish tip on effected cylinders

 

[2014 Z51]

Thank you for your input.
I did check the compression but, I will check it again.
FYI:
I put a long block in this truck about 60,000 miles ago.