What is the best way to troubleshoot engine misfire in a Ford Focus?

Recently my Ford Focus has been experiencing engine misfires. I've tried changing the spark plugs, but it hasn't seemed to make a difference. What other steps can I take to diagnose and fix this issue?

First, check the ignition coils to see if they are functioning properly. If they are not, they may need to be replaced. Also, make sure the fuel injectors are clean and functioning correctly. If the issue persists, consider getting a diagnostic test done at a mechanic.

Another possible cause could be a faulty engine sensor. Have a mechanic take a look and run a diagnostic test to pinpoint the issue. They may need to replace the sensor to fix the misfire.

Make sure to also check the air filter and PCV valve, as they can contribute to misfires if dirty or malfunctioning. Keeping up with regular maintenance for these components can also prevent future issues.