Toyota Corolla E140 (2006-2013) how to fix P0300 misfire code

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Replace Spark Plugs

• Tools Required: Socket set, torque wrench, spark plug socket.
• Instructions:
  1. Remove the engine cover if applicable.
  2. Disconnect the ignition coils from each spark plug.
  3. Using the spark plug socket, carefully unscrew the old spark plugs.
  4. Inspect the old plugs for wear; replace with new plugs if worn.
  5. Install new spark plugs by hand, then torque to the manufacturer's specifications (typically around 13-15 lb-ft).
  6. Reconnect the ignition coils.

3. Inspect/Replace Ignition Coils

• Tools Required: Socket set, multimeter (for testing).
• Instructions:
  1. Remove the ignition coils from the engine.
  2. Check the coil resistance using a multimeter; it should fall within the manufacturer specifications.
  3. Replace any faulty ignition coils with new ones.
  4. Reinstall the ignition coils and reconnect the wiring.

4. Fuel Injector Inspection

• Tools Required: Fuel pressure gauge, injector cleaner.
• Instructions:
  1. Disconnect the fuel pump relay and start the engine to relieve fuel pressure.
  2. Connect a fuel pressure gauge to the fuel rail and check the pressure against specifications.
  3. If low, inspect and replace the fuel filter if necessary.
  4. Use injector cleaner or replace fuel injectors if they are clogged or malfunctioning.

5. Vacuum Leak Inspection

• Tools Required: Smoke machine or carburetor cleaner.
• Instructions:
  1. Conduct a smoke test on the intake system to identify leaks.
  2. If no smoke machine is available, spray carburetor cleaner around vacuum lines while the engine is running; listen for changes in RPM.
  3. Replace any damaged vacuum lines or gaskets.

6. Compression Test

• Tools Required: Compression tester.
• Instructions:
  1. Remove spark plugs to allow for easier cranking.
  2. Insert the compression tester into the spark plug hole of each cylinder.
  3. Crank the engine and note the compression readings; they should be within manufacturer specifications (usually 180-220 psi).
  4. If any cylinder shows lower compression, further investigation into the engine internals may be necessary.