HELP Cylinder 4 Misfire (P0304)

[Tyler_K02]

I recently got a used 2014 Fiesta ST and right after I got it it started to misfire and gave me a P0304 DTC. I've replaced all the sparkplugs and confirmed its not the ignition coils, I know it could be the fuel injectors but before i spend more money I want some help/advice on what else could cause my misfire.

 

[SteveS]

Did you move the #4 coil pack to another cylinder to test it?
The plug wires can also be a cause of this.
If you have the ability to check fuel trims you can determine if it's from fueling.

In my experience with coil pack equipped vehicles, it is most often the coil pack that causes this. A 2014 car has enough miles on it that replacing all the coil packs wouldn't be a bad idea anyway.

 

[Tyler_K02]

I did move the #4 coil pack to cylinder 3 and #3 coil pack to cylinder 4 and the misfire continued on cylinder 4 and I was able to confirm it's not the plug wires although I am unable to check the fuel trims.

 

[JJ_FiestaST]

Compression test? You can buy a tester cheap. Maybe buy/rent a camera probe to look inside the cylinder to look for damage and/or a valve stuck open.

 

[TyphoonFiST]

What did the Plugs that came out look like?