my Ford F-150 Fourteenth Generation (2021-present) has a check engine light and shows a P0303 code

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

Solution

1. Preparation

• Gather tools: OBD-II scanner, spark plug socket, ratchet set, compression tester, multimeter, fuel injector cleaning kit.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Replace Spark Plug and Ignition Coil

• Sub-steps:
  1. Disconnect the battery to prevent electrical shorts.
  2. Remove the engine cover if applicable.
  3. Remove the ignition coil from cylinder 3 by unscrewing the mounting bolts and disconnecting the electrical connector.
  4. Use a spark plug socket to remove the spark plug from cylinder 3.
  5. Inspect the old spark plug for signs of damage or fouling.
  6. Install a new spark plug (torque to manufacturer's specification, typically around 13-15 lb-ft).
  7. Install the new ignition coil and reconnect the electrical connector.

3. Inspect and Clean Fuel Injector

• Sub-steps:
  1. Disconnect the fuel injector connector for cylinder 3.
  2. Remove the fuel rail (if necessary) to access the injector.
  3. Remove the fuel injector and inspect for clogs or damage.
  4. If clogged, clean the injector using a fuel injector cleaning kit or replace it as necessary.
  5. Reinstall the fuel injector, ensuring it seats properly.
  6. Reconnect the fuel rail and injector connectors.

4. Perform Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 3.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine for several seconds to obtain a reading.
  4. Compare the reading to the manufacturer's specifications (typically between 100-150 psi).
  5. If compression is low, further investigation into valve seating or piston ring condition may be needed.