how to fix P0304 misfire code on Volkswagen Golf MK5 (2004-2008)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the engine is cool before starting.

2. Inspect Spark Plug and Ignition Coil

• Remove the engine cover if applicable.
• Disconnect the ignition coil connector from the coil on cylinder 4.
• Remove the ignition coil using a socket set.
• Inspect the spark plug; if worn or fouled, replace it.
• Replace the ignition coil if damaged or not functioning correctly.

3. Check Fuel Injector

• Disconnect the fuel injector connector for cylinder 4.
• Test the injector resistance using a multimeter (should be within specified range).
• If the injector is faulty, replace it with a new one.
• Reconnect the fuel injector connector.

4. Compression Test

• Remove all spark plugs to facilitate compression testing.
• Insert the compression tester into the spark plug hole of cylinder 4.
• Crank the engine and record the compression reading.
• Compare with manufacturer specifications; if low, further investigation is needed (possible valve or head gasket issues).

5. Inspect for Vacuum Leaks

• Visually check vacuum hoses connected to the intake manifold for cracks or disconnections.
• Use an aerosol spray (like brake cleaner) around the intake area while the engine is idling; a change in RPM indicates a vacuum leak.
• Repair or replace any damaged hoses.

6. Reassemble and Test

• Reinstall the spark plugs and ignition coils securely.
• Reconnect the negative battery terminal.
• Start the engine and allow it to reach operating temperature.