my Ford F-150 has a misfire code P0303, what should I check

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 and parts required for the repair.
• Disconnect the battery to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Compression tester
• Fuel injector cleaning kit (if applicable)

2. Replace Spark Plug

• Sub-steps:
  1. Remove the ignition coil from cylinder 3 by disconnecting the electrical connector and unscrewing the retention bolts.
  2. Remove the spark plug using a socket wrench, and inspect it for signs of wear, fouling, or damage.
  3. Install a new spark plug, ensuring it is gapped correctly according to manufacturer specifications (typically 0.054 inches for Ford F-150).
  4. Torque the spark plug to the manufacturer’s specification (usually around 13 lb-ft).
  5. Reinstall the ignition coil and reconnect the electrical connector.

3. Inspect and Replace Ignition Coil

• Sub-steps:
  1. If the spark plug appears in good condition, test the ignition coil using a multimeter to ensure it meets resistance specifications.
  2. If faulty, remove the ignition coil and replace it with a new one.
  3. Reinstall the coil and reconnect the electrical connector.

4. 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 and record the compression reading.
  4. If the compression is below manufacturer specifications (usually around 120-150 psi), further inspection of the cylinder head, valves, or piston rings may be necessary.

5. Inspect and Clean Fuel Injector

• Sub-steps:
  1. Remove the fuel injector from cylinder 3.
  2. Inspect for clogs or debris.
  3. Clean the injector using a fuel injector cleaning kit or replace it if it is defective.
  4. Reinstall the fuel injector ensuring proper sealing.