how to fix P0300 random misfire code on my Toyota Highlander XU70 (2020-Present)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.

2. Spark Plug Replacement

1. Remove Engine Cover (if applicable)

   • Tools: Socket set
   • Unscrew and lift off the engine cover.

2. Remove Spark Plugs

   • Tools: Socket wrench with a spark plug socket
   • Disconnect the ignition coil connectors and remove the coils.
   • Use the spark plug socket to remove the spark plugs. Inspect for wear or carbon buildup.

3. Install New Spark Plugs

   • Install new spark plugs using the manufacturer’s specified torque (typically around 13-20 lb-ft).
   • Reinstall ignition coils and reconnect connectors.

3. Ignition Coil Inspection and Replacement

1. Inspect Ignition Coils

   • Check for cracks or carbon tracking.
   • Tools: Multimeter
   • Test the resistance of each coil; replace any that are out of specification.

2. Install New Ignition Coils

   • Tools: Socket set
   • Position the new coils over the spark plugs and secure them.

4. Fuel Injector Cleaning/Replacement

1. Test Fuel Injectors

   • Connect a fuel pressure gauge to check fuel pressure. Ensure it meets manufacturer specifications.
   • Use a noid light to check for signal at the injector connectors.

2. Clean or Replace Fuel Injectors

   • If cleaning, use an injector cleaner kit as per instructions.
   • If replacement is necessary, disconnect fuel lines and electrical connectors, then remove the old injectors and install new ones.

5. Address Vacuum Leaks

1. Inspect Vacuum Lines

   • Check all vacuum hoses for cracks or disconnections.
   • Tools: Visual inspection and smoke tester (if available).

2. Repair or Replace Leaky Hoses

   • Replace any damaged hoses and secure all connections.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Fuel pressure gauge
• Noid light
• Smoke machine (optional)

Parts Required:

• Spark plugs (OEM recommended)
• Ignition coils (if faulty)
• Fuel injectors (if clogged or faulty)
• Vacuum hoses (if damaged)

Estimated Repair Time: 2-4 hours

Safety Warnings:

• Disconnect the battery before working on electrical components.
• Allow the engine to cool before performing any work on the ignition system.