my Ford Mustang S650 (2024-Present) has a check engine light with code P0300

Solution

1. Preparation

• Gather all necessary tools and parts.
• Park the vehicle on a level surface and engage the parking brake.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Spark Plugs

1. Remove the engine cover if applicable.
2. Use a socket wrench to remove the spark plug wires or ignition coils.
3. Carefully remove the spark plugs using a spark plug socket.
4. Check the condition of each spark plug; replace any that are worn or fouled.
5. Set the gap on new spark plugs to the manufacturer’s specification (typically between 0.028 to 0.060 inches for Mustangs).
6. Reinstall the spark plugs and reconnect the ignition coils or spark plug wires.

3. Check and Replace Ignition Coils

1. Disconnect the electrical connector from each ignition coil.
2. Remove the ignition coils using a socket wrench.
3. Inspect the coils for cracks or damage; replace any faulty coils.
4. Install new ignition coils and reconnect the electrical connectors.

4. Inspect Fuel Injectors

1. Disconnect the fuel pump relay to relieve fuel pressure.
2. Remove the intake manifold if necessary to access the fuel injectors.
3. Check each injector for clogs or leaks and clean or replace as needed.
4. Reinstall the intake manifold and reconnect the fuel pump relay.

5. Address Vacuum Leaks

1. Inspect all hoses and connections in the intake system.
2. Use a smoke machine or carburetor cleaner to check for leaks.
3. Replace any damaged hoses or connections.

6. Perform Compression Test

1. Remove the spark plugs from each cylinder.
2. Insert a compression gauge into each spark plug hole.
3. Crank the engine and record the compression readings for each cylinder; compare with manufacturer specifications.
4. Address any cylinders with low compression by checking for valve issues or piston damage.