how to diagnose a misfire in my Ford F-150 13th Generation (2015-2020)

Learn how to diagnose and fix engine misfires (P0300-P0308) in Ford F-150 (2015-2020). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, fuel pressure gauge, multimeter, compression tester.
• Disconnect the battery to prevent electrical shorts.
• Allow the engine to cool before working on it.

2. Replace Spark Plugs and Ignition Coils

• Remove the engine cover (if applicable) using a socket set.
• Disconnect the ignition coil connectors from each affected cylinder.
  • Safety Warning: Ensure battery is disconnected before handling electrical components.
• Remove the ignition coils by unscrewing them and pulling them out.
• Remove the spark plugs using a spark plug socket.
• Install new spark plugs and torque them to the manufacturer's specifications (typically around 13-15 lb-ft).
• Replace ignition coils, ensuring they are seated properly and reconnect the electrical connectors.

3. Fuel System Inspection

• Tools Required: Fuel pressure gauge.
• Locate the fuel rail and connect the fuel pressure gauge to the Schrader valve.
• Turn the ignition key to the "ON" position (do not start the engine) to check the fuel pressure.
• Ensure the pressure is within the manufacturer’s specifications (typically around 30-50 PSI).
• If pressure is low, inspect the fuel pump and filter and replace as necessary.

4. Compression Test

• Tools Required: Compression tester.
• Remove the spark plugs to access the cylinder heads.
• Insert the compression tester into the spark plug hole of each cylinder.
• Crank the engine several times and record the compression readings.
• Compare the readings with the manufacturer’s specifications; if any cylinder is significantly lower, further investigation is required (possible head gasket issues).