how to fix the P0304 misfire code in my Volkswagen Golf MK6 (2009-2014)

Solution

1. Preparation

• Gather tools and parts required.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the negative battery terminal to ensure safety.

2. Inspect and Replace Spark Plug

• Tools Required: Spark plug socket, ratchet, torque wrench.
• Remove the ignition coil from cylinder 4.
• Remove the spark plug using a spark plug socket.
• Inspect the spark plug for wear, carbon deposits, or damage; if damaged, replace it with a new one.
• Torque the new spark plug to the manufacturer’s specification (typically around 22 ft-lbs).
• Reinstall the ignition coil.

3. Check and Replace Ignition Coil

• If the spark plug is fine, test the ignition coil by swapping it with a working coil from another cylinder.
• Clear the P0304 code and run the engine to see if the misfire moves to the swapped cylinder; if it does, replace the faulty ignition coil.
• If replacing, torque the new ignition coil to specifications and ensure the connector is secure.

4. Inspect and Clean Fuel Injector

• If the ignition coil is functioning correctly, check the fuel injector for cylinder 4.
• Remove the fuel injector connector and inspect for corrosion or damage.
• Use a noid light to check if the injector is receiving a signal; if no signal, inspect wiring and connections.
• If the injector is faulty, replace it with a new one, ensuring proper seating and secure connections.

5. Perform Compression Test

• If misfire persists, perform a compression test on cylinder 4.
• Remove spark plugs from all cylinders to allow for equal testing.
• Insert the compression gauge into the spark plug hole of cylinder 4 and crank the engine.
• Compare the compression reading to manufacturer specifications (typically around 150-200 psi); if low, further diagnosis of valves or piston rings may be needed.