why is my Toyota Corolla E210 (2019-2024) engine misfiring

Learn how to diagnose and fix engine misfire issues (P0301-P0304) in Toyota Corolla E210 (2019-2024). Step-by-step guide with diagnostic procedures and repair instructions.

Solution

1. Preparation

• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the negative battery terminal to ensure electrical safety.

2. Replace Spark Plugs

• Tools Required: Socket set, torque wrench, spark plug socket.
• Remove the ignition coil cover if applicable.
• Unplug the ignition coils from the spark plugs.
• Use a spark plug socket to carefully remove old spark plugs.
• Inspect and replace with new spark plugs, ensuring the correct gap is set (typically around 0.044 inches for most Toyota models).
• Torque new spark plugs to manufacturer specifications (usually around 13 lb-ft).
• Reinstall ignition coils and cover.

3. Check and Replace Ignition Coils (if necessary)

• Remove the ignition coils one at a time from the engine.
• Inspect for cracks or signs of wear.
• Replace any faulty ignition coils with new ones, ensuring they are seated properly.
• Reconnect the wiring harness to each ignition coil.

4. Inspect and Replace Fuel Injectors (if necessary)

• Disconnect the fuel pump relay and crank the engine to relieve fuel pressure.
• Remove the fuel rail by unscrewing bolts and gently lifting it off, taking care not to damage the fuel injectors.
• Pull out the injectors from the rail and inspect them for clogs or leaks.
• Replace any faulty injectors with new ones, applying a small amount of lubricant to the O-rings before installation.
• Reassemble the fuel rail and reconnect the fuel pump relay.

5. Verify Engine Compression

• Remove spark plugs for access.
• Insert a compression tester into the spark plug hole.
• Crank the engine to take a reading and compare against manufacturer specifications (generally around 180-200 psi).
• If readings are low, further diagnostics may be required for valve or piston issues.