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

Solution

1. Preparation

• Gather tools and materials: OBD-II scanner, multimeter, socket set, torque wrench, replacement spark plugs, ignition coils (if needed), fuel injector cleaner.
• Ensure the vehicle is parked on a level surface and the engine is cool.

2. Replace Spark Plugs

• Step 1: Remove the engine cover (if applicable) using a socket set.
• Step 2: Disconnect the ignition coil connectors.
• Step 3: Remove the ignition coils by unscrewing them from the engine.
• Step 4: Unscrew the spark plugs using a spark plug socket and ratchet.
• Step 5: Install new spark plugs, ensuring they are gapped to manufacturer specifications (typically around 0.044 inches for Honda).
• Step 6: Reinstall the ignition coils and reconnect the connectors.
• Step 7: Replace the engine cover.

3. Test Ignition Coils

• Step 1: Set the multimeter to measure resistance.
• Step 2: Disconnect each ignition coil and measure the resistance across the terminals.
• Step 3: Compare the readings with manufacturer specifications (typically 0.4 - 0.8 ohms for primary and several kilo-ohms for secondary).
• Step 4: Replace any faulty ignition coils.

4. Clean or Replace Fuel Injectors

• Step 1: If using fuel injector cleaner, add it to the fuel tank as per the product instructions.
• Step 2: For removal, disconnect the fuel lines and electrical connectors.
• Step 3: Remove the fuel rail and injectors from the engine.
• Step 4: Clean the injectors with an ultrasonic cleaner or replace with new ones.
• Step 5: Reinstall the fuel injectors and fuel rail, ensuring proper sealing.

5. Verify Compression

• Step 1: Remove all spark plugs again to gain access to the cylinders.
• Step 2: Insert the compression tester into the spark plug hole of each cylinder.
• Step 3: Crank the engine while observing the compression gauge.
• Step 4: Compare the readings with manufacturer specifications (typically around 190-220 psi for Honda).
• Step 5: Address any cylinders with significantly lower compression.