Basically, the diagnostic codeP0304 OBD2 indicates that a misfire has been detected. This fault originates specifically in the cylinder number 4. It should be noted that, together with this code, codes related to misfire can be established.
The ECM (Engine Control Module) constantly monitors the proper functioning of all cylinders to ensure that everyone is firing in time.
To solve all the problems caused by the DTC code P0304 you could do the following:
If the motor is unstable, you should check the entire cable system as well as its connectors that lead to the cylinders. Take into account that ignition components - such as spark plugs, spark plug wires, distributor cap - need to be replaced over time, as they deteriorate due to use.
If you notice a strange smell coming from the exhaust, it may mean that the Three-Way Catalyst (TWC) is having problems. That's why you can change the cat.
One of the fuel injectors may be defective, repaired or changed if necessary.