How do you diagnose misfiring engine?

To diagnose a misfiring engine, start by checking for diagnostic trouble codes (DTCs) using an OBD-II scanner, which can pinpoint specific cylinder issues. Next, inspect the spark plugs, ignition coils, and fuel injectors for signs of wear or malfunction. Additionally, assess the engine's vacuum lines for leaks and examine the fuel system for proper pressure and flow. Finally, conduct a compression test to evaluate the health of each cylinder.