how to fix P0300 random misfire code in Toyota Highlander XU70 (2020-Present)

Solution

1. Preparation

• Gather all necessary tools and parts.
• Park the vehicle on a level surface and set the parking brake.
• Disconnect the negative terminal of the battery to ensure safety.

2. Inspect and Replace Spark Plugs

• Tools Required: Spark plug socket, ratchet, torque wrench.
• Remove the ignition coil covers if applicable.
• Use the spark plug socket to remove the spark plugs.
• Inspect each spark plug for wear and carbon buildup; replace any that are damaged.
• Gap new spark plugs to the manufacturer’s specifications (typically between 0.028-0.031 inches for most Toyota engines).
• Install the new spark plugs and torque them to manufacturer specifications (usually around 13 lb-ft).

3. Check and Replace Ignition Coils

• Tools Required: Socket set, torque wrench.
• Disconnect the electrical connector from each ignition coil.
• Remove the ignition coils from the spark plugs and inspect for cracks or carbon tracking.
• If any coils are faulty, replace them with new ones.
• Reinstall the ignition coils and reconnect the electrical connectors. Torque them to manufacturer specifications (typically around 9 lb-ft).

4. Inspect and Clean Fuel Injectors

• Tools Required: Fuel injector cleaning kit or professional service.
• Check fuel pressure with a gauge to ensure it meets specifications (usually around 50-60 psi).
• If the injectors are clogged, use a fuel injector cleaning kit to clean them.
• Alternatively, replace any faulty injectors with new units.

5. Inspect Vacuum Lines

• Tools Required: Visual inspection tools.
• Conduct a thorough visual inspection of all vacuum lines connected to the intake manifold.
• Replace any cracked or damaged vacuum hoses to prevent air leaks.

6. Compression Test

• Tools Required: Compression tester.
• Remove all spark plugs and connect the compression tester to each cylinder.
• Crank the engine and record the compression readings.
• Compare the readings to the manufacturer’s specifications; if any cylinder is significantly low, further investigation is needed.