how to fix the P0304 code on my 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

• Gather tools and parts needed for the repair.
• Ensure the vehicle is parked on a level surface, and the engine is cool.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plug

• Sub-steps:
  • Remove the ignition coil from cylinder 4 by unscrewing the mounting bolt and disconnecting the electrical connector.
  • Remove the spark plug using a socket wrench and a spark plug socket.
  • Inspect the spark plug for wear or fouling. Replace it if necessary with a new spark plug recommended for your vehicle.
  • Reinstall the spark plug and torque it to the manufacturer specifications (typically around 13-15 lb-ft).
  • Reattach the ignition coil.

3. Inspect and Replace Ignition Coil

• Sub-steps:
  • If the spark plug is in good condition, test the ignition coil for proper function using a multimeter.
  • If faulty, remove the ignition coil and replace it with a new one.
  • Ensure the new ignition coil is seated properly and the connector is reattached securely.

4. Check and Clean Fuel Injector

• Sub-steps:
  • Disconnect the fuel injector connector for cylinder 4.
  • Perform a resistance check on the fuel injector using a multimeter; replace if out of specification.
  • If the injector is functioning, clean it using a fuel injector cleaner or ultrasonic cleaning method before reinstallation.
  • Reconnect the fuel injector connector.

5. Verify and Repair Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum hoses and intake manifold for cracks or disconnections.
  • Use a smoke machine or carburetor cleaner to detect leaks while the engine is running.
  • Replace any damaged hoses or reseal the intake manifold if necessary.