how to fix P0300 random misfire code in Toyota Corolla E170 (2013-2019)

Solution

1. Preparation

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

2. Replace Spark Plugs

• Tools Required: Spark plug socket, ratchet, torque wrench, dielectric grease.
• Remove the spark plug wires or ignition coils carefully.
• Use the spark plug socket to remove the old spark plugs.
• Inspect the old plugs for damage or excessive wear.
• Apply dielectric grease to the threads of the new spark plugs and install them with a torque of 13 ft-lbs (17.6 Nm).
• Reconnect the spark plug wires or ignition coils securely.

3. Inspect and Replace Ignition Coils (if necessary)

• Tools Required: Ratchet, socket set.
• Remove the ignition coils from the spark plugs carefully.
• Using a multimeter, check the resistance of each coil; replace any that do not meet specifications (typically around 0.5 to 1.5 ohms for primary resistance).
• Install new ignition coils by reversing the removal process, ensuring they are seated properly.

4. Check and Clean Fuel Injectors

• Tools Required: Fuel pressure gauge, injector cleaning kit (if cleaning is necessary).
• Connect the fuel pressure gauge to the fuel rail and check for proper fuel pressure (usually between 40-50 psi).
• If pressure is low, inspect the fuel filter and pump.
• If injectors are clogged, use an injector cleaning kit or replace them if necessary.

5. Inspect for Vacuum Leaks

• Tools Required: Smoke machine (optional) or carburetor cleaner.
• Visually inspect all vacuum hoses and the intake manifold for cracks or loose connections.
• If using a smoke machine, introduce smoke into the intake system and look for leaks.
• Repair or replace any damaged vacuum hoses or gaskets.

6. Perform Compression Test

• Tools Required: Compression tester.
• Remove all spark plugs.
• Insert the compression tester into the first cylinder and crank the engine to get a reading.
• Repeat for each cylinder; readings should generally be between 180-200 psi.
• If any cylinder shows significantly lower compression, further investigation may be needed for internal engine issues.