how to deal with a P0304 code on my Volkswagen Golf MK5 (2004-2008)

Solution

1. Preparation

• Gather tools and parts required for repairs.
• Disconnect the negative battery terminal to prevent electrical shock.

2. Replace Spark Plug

1. Remove the engine cover (if applicable).
2. Disconnect the ignition coil connector from cylinder 4.
3. Remove the ignition coil by unscrewing it and gently pulling it out.
4. Remove the spark plug using a spark plug socket and ratchet.
5. Inspect the old spark plug for wear or damage; replace if necessary.
6. Install the new spark plug and torque to 20 Nm (15 ft-lbs).
7. Reinstall the ignition coil and reconnect the electrical connector.

3. Replace Ignition Coil (if needed)

1. If the coil was found faulty during inspection, proceed with replacement.
2. Remove the ignition coil as described above.
3. Install the new ignition coil in place and secure it with screws.
4. Reconnect the ignition coil connector.

4. Inspect and Clean Fuel Injector

1. Access the fuel injector for cylinder 4 by removing any necessary components (i.e., intake manifold).
2. Disconnect the fuel injector connector and the fuel line.
3. Remove the fuel injector from the rail.
4. Inspect for clogs or dirt; clean or replace if necessary.
5. Reinstall the fuel injector and reconnect the fuel line and connector.

5. Compression Test (if misfire persists)

1. Remove the spark plug for cylinder 4.
2. Insert the compression gauge into the spark plug hole.
3. Crank the engine a few times to take a reading.
4. Compare the reading with specifications (typically around 10-15 bar); replace cylinder head gasket or piston rings if compression is low.