how to fix P0304 code in 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 required for the repair.
• Disconnect the battery to prevent electrical shock.
• Ensure the engine is cool before beginning work.

2. Inspect and Replace Spark Plug

• Remove the ignition coil from cylinder 4:
  • Disconnect the electrical connector.
  • Remove the mounting bolts using a socket set.
• Remove the spark plug from cylinder 4:
  • Use a spark plug socket to carefully unscrew the spark plug.
  • Inspect for wear, fouling, or damage.
• Install the new spark plug:
  • Torque the new spark plug to the manufacturer-recommended specifications (typically around 13-15 lb-ft).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Check and Replace Ignition Coil (if necessary)

• If the spark plug is in good condition, test the ignition coil:
  • Use a multimeter to measure resistance according to the specifications (typically 0.4-2.0 ohms for primary winding and 6,000-12,000 ohms for secondary winding).
• Replace the ignition coil if it is out of specification:
  • Install the new ignition coil and secure it with mounting bolts.
  • Reconnect the electrical connector.

4. Inspect and Test Fuel Injector

• Remove the fuel injector from cylinder 4:
  • Disconnect the electrical connector and fuel lines.
  • Unscrew the mounting bolts if applicable.
• Test the injector operation using a noid light:
  • If it does not flash, consider replacing the injector.
• Reinstall the fuel injector and reconnect the fuel lines and connector.

5. Compression Test (if required)

• If misfire persists, perform a compression test on cylinder 4:
  • Remove the spark plug and install a compression gauge.
  • Crank the engine and record the compression reading.
• If compression is low, further investigation is needed for potential internal engine issues (valves, piston rings).