how to fix P0300 random misfire code in Honda Civic 10th Generation (2016-2021)

Solution

1. Preparation

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

2. Replace Spark Plugs

• Remove the ignition coil cover if applicable.
• Use a socket wrench to remove the spark plug using a spark plug socket.
• Inspect the spark plugs for wear; replace with OEM-spec plugs as necessary.
• Torque the new spark plugs to manufacturer specifications (typically 13-16 lb-ft).
• Reattach the ignition coil and cover.

3. Check and Replace Ignition Coils

• Disconnect the electrical connectors from the ignition coils.
• Remove the coils using a socket wrench if they appear faulty or if misfires persist.
• Replace with new ignition coils, ensuring they are seated properly.
• Reconnect the electrical connectors securely.

4. Inspect and Clean Fuel Injectors

• Remove the fuel rail if necessary to access the injectors.
• Inspect injectors for clogs using a noid light to check for proper operation.
• Clean injectors using a dedicated injector cleaner or replace them if necessary.
• Reassemble the fuel rail and ensure all connections are tight.

5. Perform Fuel Pressure Test

• Attach a fuel pressure gauge to the fuel rail test port.
• Turn the ignition to the ON position (do not start) to check pressure; it should meet specifications (usually around 40-50 psi).
• If pressure is low, inspect the fuel pump and fuel filter for issues.

6. Inspect Vacuum Lines

• Visually inspect all vacuum lines for cracks, loose connections, or damage.
• Replace or repair any damaged lines.
• Start the engine to check for any hissing sounds indicating a vacuum leak.