how to diagnose P0303 misfire code on my Ford F-150 12th Generation (2009-2014)

Learn how to diagnose and fix P0303 cylinder 3 misfire in Ford F-150 12th Generation. Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather tools and parts.
• Disconnect the battery to prevent electrical shorts.
• Ensure the engine is cool before starting work.

2. Inspect and Replace Spark Plug

• Remove the spark plug from cylinder 3 using a socket wrench.
• Inspect the spark plug for signs of wear, carbon buildup, or damage.
• Replace with a new spark plug (part number as per manufacturer specifications).
  • Torque the new spark plug to the manufacturer's specified value, typically around 13-15 lb-ft.

3. Check and Replace Ignition Coil

• Disconnect the electrical connector from the ignition coil on cylinder 3.
• Remove the ignition coil using a socket wrench.
• Inspect for cracks or wear.
• Replace with a new ignition coil if defective.
  • Reinstall and torque to the manufacturer's specifications.

4. Fuel Injector Inspection

• Disconnect the fuel injector connector for cylinder 3.
• Use a noid light to check for proper electrical signal to the injector.
• If no signal is detected, trace wiring for faults or replace the injector.
• If the injector is faulty, replace it with a new one, ensuring correct seating and connections.

5. Compression Testing

• Remove the spark plug from cylinder 3.
• Insert a compression gauge into the spark plug hole.
• Crank the engine and record the compression reading.
  • Compare the reading with manufacturer specifications; typically, it should be around 120-150 psi.
• If compression is low, further investigation into internal engine components may be necessary.