Q: P0304 Misfiring on Cylinder 4

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My truck has been misfiring on the number 4 cylinder. And I have changed the coil pack and plug which has voltage across the plug of the injector. I’m also getting this code P0304. It use to come on periodically, but now the code stays on permanently. Do you know how to fix this?

Hello. If the spark plug and the coil have been replaced, then a compression test needs to be done. It is common for the valve seat to fail and cause this. When it fails, it causes low compression which then causes the misfire. If the compression is fine, then it is possibly a fuel injector issue, but that is not common for this vehicle. If you want to have this fixed, consider YourMechanic, as a certified technician can come to your home or office to diagnose the misfiring problem and resolve the issue.

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