how to fix P0304 misfire code on Ford F-150 13th Generation (2015-2020)

Learn how to diagnose and fix P0304 cylinder 4 misfire in Ford F-150 (2015-2020). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Allow the engine to cool if it has been running.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the ignition coil cover if applicable.
• Disconnect the electrical connector from the ignition coil.
• Remove the ignition coil from cylinder 4.
• Use a spark plug socket to remove the spark plug.
• Inspect the spark plug gap; replace with a new spark plug if worn or damaged.
• Install the new spark plug and torque it to the manufacturer’s specifications (usually around 13-15 ft-lbs).
• Reinstall the ignition coil and connect the electrical connector.

3. Inspect and Replace Ignition Coil (if necessary)

• If the spark plug is fine, proceed to check the ignition coil.
• Swap the ignition coil from cylinder 4 with another cylinder (e.g., cylinder 2).
• Clear the codes and perform a test drive.
• If the misfire moves to the new cylinder, replace the ignition coil for cylinder 4.

4. Inspect Fuel Injector (if necessary)

• If the misfire persists, check the fuel injector.
• Disconnect the fuel injector connector for cylinder 4.
• Use a noid light to test for signal. If there’s no signal, check the wiring.
• If the injector is not functioning, replace it.

5. Compression Test (if necessary)

• If the misfire continues, perform a compression test on cylinder 4.
• Remove the spark plug and insert the compression tester.
• Crank the engine and read the compression. It should be within the manufacturer’s specifications (typically around 120-150 psi).
• If compression is low, further engine diagnostics may be required.