how to diagnose a misfire in my Toyota Corolla E170 (2013-2019) that's showing P0301 code?

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, multimeter, compression tester.
• Safety Warnings: Disconnect the battery before working on electrical systems. Allow the engine to cool before performing any work.

2. Replace Spark Plug

• Sub-steps:
  1. Remove the engine cover (if applicable) using a socket set.
  2. Disconnect the ignition coil connector for cylinder 1.
  3. Remove the ignition coil from cylinder 1.
  4. Use the spark plug socket to remove the spark plug from cylinder 1.
  5. Install a new spark plug (ensure it is gapped correctly as per manufacturer specifications).
  6. Reinstall the ignition coil and reconnect the connector.

3. Replace Ignition Coil (if necessary)

• Sub-steps:
  1. If the ignition coil is faulty, remove it from cylinder 1 (follow steps 2 and 3 from the previous section).
  2. Install a new ignition coil for cylinder 1.
  3. Reconnect the ignition coil connector.

4. Clean/Replace Fuel Injector

• Sub-steps:
  1. If the fuel injector is found to be faulty, remove the fuel rail (ensure to relieve fuel pressure before removal).
  2. Remove the fuel injector from cylinder 1.
  3. Clean the injector using a specialized cleaner or replace it with a new injector.
  4. Reinstall the fuel rail and reconnect any electrical connectors.

5. Perform Compression Test (if necessary)

• Sub-steps:
  1. Remove the spark plug from cylinder 1.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine and note the compression reading; it should be within the manufacturer's specified range.
  4. If compression is low, further investigation into internal engine components may be necessary.