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 needed for the repair.
• Disconnect the battery to ensure safety while working on electrical components.

2. Replace Spark Plug

• Remove the ignition coil from cylinder 4 by unscrewing the bolts and disconnecting the electrical connector.
• Remove the spark plug using a spark plug socket and ratchet.
• Inspect the old spark plug for wear; if it's fouled or damaged, replace it with a new spark plug (OEM recommended gap).
• Reinstall the new spark plug and torque it to the manufacturer's specification (typically around 13-15 lb-ft).
• Reinstall the ignition coil and reconnect the electrical connector.

3. Replace Ignition Coil

• If the ignition coil showed signs of damage, remove it as described above.
• Install a new ignition coil and torque it to the manufacturer's specification (usually 7-9 lb-ft).
• Reconnect the electrical connector to the ignition coil.

4. Test Fuel Injector

• If the spark plug and ignition coil are functioning properly, check the fuel injector.
• Disconnect the fuel injector electrical connector and test for voltage with a multimeter while cranking the engine.
• If the injector is not receiving power, check the wiring or replace the injector if it is faulty.

5. Compression Test (If Needed)

• If misfire persists, perform a compression test on cylinder 4.
• Remove the spark plug and install the compression tester.
• Crank the engine and record the compression reading; it should be within manufacturer specifications.
• If low, further investigation into valve seals or piston rings may be needed.