how to fix P0304 misfire code on my Ford F-150 14th Generation (2021-2024)

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

Solution

1. Preparation

• Gather all necessary tools and parts.
• Disconnect the negative battery terminal.
• Ensure the engine is cool before starting work.

2. Inspect Ignition Components

• Tools Required: Socket set, torque wrench
• Remove the engine cover (if applicable) using a socket set.
• Carefully disconnect the ignition coil connector for cylinder 4.
• Remove the ignition coil using a socket, and inspect for cracks or damage.
• Replace the spark plug in cylinder 4 if it shows signs of wear or fouling. Use a spark plug gap tool to ensure proper gap (typically 0.030-0.035 inches).
• Reinstall the ignition coil and reconnect the connector. Torque the coil to manufacturer specifications.

3. Check Fuel Injector

• Tools Required: Fuel injector cleaning kit or replacement injector
• With the ignition off, disconnect the fuel injector connector for cylinder 4.
• If cleaning, use a fuel injector cleaning kit to flush the injector. If replacing, remove the old injector and install a new one, ensuring it is properly seated.
• Reconnect the fuel injector connector.

4. Compression Test

• Tools Required: Compression tester
• Remove the spark plug from cylinder 4.
• Insert the compression tester into the spark plug hole and crank the engine for several seconds.
• Compare the compression reading to the specifications (typically 120-150 psi). If low, further engine diagnostics may be necessary.

5. Inspect for Vacuum Leaks

• Tools Required: Smoke machine or carburetor cleaner
• Use a smoke machine to check for vacuum leaks around the intake manifold. If no smoke machine is available, spray carburetor cleaner around the intake area while the engine is running and listen for changes in RPM.
• Repair any identified leaks.

6. Final Assembly

• Once all components have been checked and repaired, reassemble any parts removed during the process.
• Reconnect the negative battery terminal.