Q: I need help to solve the code p0304 on my 2007 mustang gt i changed the coil and the sparkplug and the check engine light is still

Hello, thank you for writing in. You started out in the right direction as spark is typically what you check first when you have a misfire. With that out of the way, you do want to scan the vehicle again to make sure a new code did not come up. If spark is not an issue, then the fuel may be. You will want to make sure the fuel injector is working on cylinder 4. If the injector is allowing an improper amount of fuel into the cylinder, combustion will be off causing a misfire. If the valves are not working correctly as well, the exhaust fumes won’t exit the chamber also causing a misfire. The issue will need to be inspected further. For more diagnostic help, contact our service department to schedule an appointment.