OBD 2 code P0303

Hello,

The P0300 or the random misfire codes can be tricky to diagnose due to this can be caused by any number of issues.

It could be due to a bad air fuel ration sensor (primary oxygen sensor), bad fuel injector or faulty circuit to the injector, low fuel pressure, faulty coil, or plugs. It can also happen due to an intake air leak.

Take a look at this guide, it covers the typical issues that cause the code:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

And what was the symptom before you changed the coils?

Also have you replaced the spark plugs?

I have attached the trouble shooting steps for the code below. Follow those steps as it can help you determine the issue.

Please let me know if you have any questions.

Thank you.