how to diagnose a misfire in my Ford F-150 14th Generation (2021-2024) with code P0303

Learn how to diagnose and fix P0303 cylinder 3 misfire in Ford F-150 (2021-2024). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the negative battery terminal to prevent accidental short circuits.

2. Inspect and Replace Spark Plug

• Tools Required: Socket set, spark plug socket, torque wrench, gap gauge.
• Remove the spark plug wire or coil connector.
• Use the spark plug socket to remove the spark plug from cylinder 3.
• Inspect the spark plug for wear, carbon deposits, or oil fouling.
• If necessary, replace the spark plug with a new one, ensuring it is gapped to manufacturer specifications (typically around 0.030 inches for Ford F-150).
• Install the new spark plug and torque it to the manufacturer’s specification (generally around 13-15 lb-ft).

3. Inspect and Replace Ignition Coil

• Tools Required: Socket set, torque wrench.
• Remove the screws or bolts securing the ignition coil to the engine.
• Lift the ignition coil straight out from the spark plug.
• Inspect the coil for signs of damage or carbon tracking.
• Replace with a new ignition coil if any issues are found, ensuring it fits properly.
• Reinstall and torque the coil down to the specified value.

4. Check Fuel Injector Operation

• Tools Required: Fuel injector cleaner kit, multimeter (if testing electrical).
• Disconnect the fuel injector connector.
• Using a multimeter, check for proper voltage and resistance according to the specifications.
• If the injector is not functioning correctly, remove it from the rail.
• Clean the injector or replace it if it is clogged or defective.

5. Perform Compression Test

• Tools Required: Compression gauge.
• Remove all spark plugs for easier cranking.
• Insert the compression gauge into the cylinder 3 spark plug hole.
• Crank the engine and note the reading.
• Compare the compression reading to the manufacturer's specifications (typically 125-175 psi).
• If compression is low, further investigation into the engine's internal components is required.