how to fix P0304 misfire code on Ford F-150 12th Generation (2009-2014)

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

• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative terminal of the battery to prevent electrical shock.
• Gather necessary tools and parts.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the ignition coil from cylinder 4 by unbolting it and disconnecting the electrical connector.
• Remove the spark plug using the spark plug socket. Inspect it for wear, cracks, or carbon buildup.
• If necessary, replace the spark plug with a new one, ensuring it is gapped correctly (usually around 0.054 inches for Ford engines).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Check and Replace Ignition Coil (if necessary)

• If the spark plug appears fine, inspect the ignition coil for cracks or damage.
• If faulty, remove the ignition coil by unscrewing it from its mounting and disconnecting the electrical connector.
• Install a new ignition coil, ensuring it is seated properly and secured with the screws.

4. Inspect Fuel Injector

• Using a noid light, check the operation of the fuel injector for cylinder 4.
• If the injector is not firing, replace it by disconnecting the electrical connector and removing the fuel rail.
• Install the new fuel injector, ensuring it is properly seated and reconnect the electrical connector.

5. Test for Vacuum Leaks

• Inspect all vacuum hoses and the intake manifold for any signs of wear or disconnection.
• Use a smoke machine or carburetor cleaner to identify any leaks.
• Replace any damaged hoses or reseal the intake manifold if necessary.