how to fix P0300 misfire code in my Toyota RAV4 Fifth Generation (2019-present)

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shock.
• Ensure the engine is cool before beginning work.

2. Inspect and Replace Spark Plugs

• Sub-steps:
  • Remove the engine cover (if applicable).
  • Use a socket set to remove the spark plug wires or ignition coil packs.
  • Remove the spark plugs using a spark plug socket.
  • Inspect the old spark plugs for wear, carbon buildup, or damage.
  • Install new spark plugs, ensuring the proper gap is set (typically around 0.044 inches for Toyota).
  • Torque the spark plugs to the manufacturer's specifications (usually around 13 lb-ft).

3. Inspect and Replace Ignition Coils (if necessary)

• Sub-steps:
  • Remove the ignition coils from the cylinder head.
  • Inspect each ignition coil for signs of damage or wear.
  • Replace any faulty ignition coils with new ones.
  • Reinstall the ignition coils and ensure they are seated properly.

4. Check Fuel System

• Sub-steps:
  • Connect a fuel pressure gauge to the fuel rail.
  • Turn the ignition to the "on" position (do not start) to check the fuel pressure.
  • Compare the reading against the manufacturer's specifications (typically 50-60 psi for RAV4).
  • If pressure is low, inspect the fuel pump and fuel filter for issues, and replace as necessary.

5. Inspect for Vacuum Leaks

• Sub-steps:
  • Visually inspect all vacuum lines for cracks or disconnections.
  • Use a smoke machine or carburetor cleaner to detect leaks while the engine is running.
  • Repair or replace any damaged vacuum lines.

6. Perform Compression Test (if needed)

• Sub-steps:
  • Remove spark plugs to allow easier access to the cylinders.
  • Insert the compression tester into the spark plug hole of each cylinder.
  • Crank the engine and record the compression readings.
  • Compare the results to the manufacturer's specifications (typically around 180-200 psi).
  • Address any cylinders with significantly lower compression.