how to fix the P0300 random misfire code on my Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the negative battery cable to ensure safety during repairs.

2. Inspect and Replace Ignition Components

• Spark Plugs

  • Remove spark plug wires or ignition coils.
  • Use a spark plug socket to remove spark plugs.
  • Inspect the spark plugs for wear or deposits. Replace if necessary (OEM specifications recommended).
  • Torque new spark plugs to manufacturer specifications (usually around 13-15 lb-ft).

• Ignition Coils

  • Inspect ignition coils for cracks or signs of wear.
  • Replace any faulty ignition coils by removing the screws and disconnecting the electrical connector.
  • Install new coils and torque screws to specification (typically around 8-11 lb-ft).

3. Fuel System Check

• Fuel Filter

  • Locate the fuel filter (if applicable) and check for clogs.
  • Replace the fuel filter if it’s dirty or clogged.

• Fuel Injectors

  • Use a fuel injector cleaner or remove and clean the injectors.
  • Ensure proper fuel injector operation using a multimeter to check resistance.

4. Address Air Intake and Vacuum Leaks

• Inspect Air Intake

  • Check the air filter and replace if dirty.
  • Inspect the intake manifold for cracks or gaps.

• Vacuum Leaks

  • Use a smoke machine or spray soapy water around hoses and connections to identify leaks.
  • Replace any damaged hoses or seals.

5. Compression Test

• If misfires persist, perform a compression test to check engine health.
  • Remove spark plugs and insert the compression tester into each cylinder.
  • Crank the engine and record compression readings. Compare against manufacturer specifications (usually around 180-200 psi).
  • If readings are low, further investigation into valve or piston issues may be required.