my Ford F-150 12th Generation (2009-2014) has a check engine light and code P0304

Learn how to diagnose and fix P0304 cylinder 4 misfire in Ford F-150 (2009-2014). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to prevent electrical shock.
• Allow the engine to cool down before starting work.

2. Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug gap tool
• Remove the engine cover if necessary.
• Disconnect the ignition coil connector from cylinder 4.
• Remove the ignition coil and set it aside.
• Remove the spark plug using a spark plug socket.
• Inspect the old spark plug for signs of wear or fouling.
• Install a new spark plug, ensuring it is gapped to the manufacturer’s specifications (typically 0.054 inches for Ford F-150).
• Torque the spark plug to the recommended specifications (typically 12-15 ft-lbs).
• Reinstall the ignition coil and reconnect the connector.

3. Inspect and Replace Ignition Coil (if necessary)

• If the ignition coil shows signs of damage during inspection, replace it.
• Tools Required: Socket set
• Remove the faulty ignition coil and replace it with a new one.
• Reconnect the ignition coil connector.

4. Test Fuel Injector (if necessary)

• If the spark plug and ignition coil are functional, check the fuel injector using a multimeter.
• Tools Required: Multimeter
• Disconnect the fuel injector connector and measure resistance.
• Compare the reading with manufacturer specifications; replace the fuel injector if it’s out of spec.

5. Verify Compression (if necessary)

• Perform a compression test on cylinder 4.
• Tools Required: Compression gauge
• Remove the spark plug from cylinder 4 and insert the compression gauge.
• Crank the engine a few times and record the reading. Compare it to the manufacturer’s specifications.
• If compression is low, further engine diagnostics may be required.