how to diagnose and fix P0301 misfire code in Toyota Corolla E170 (2013-2019)?

Solution

1. Preparation

• Tools Required: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, fuel injector cleaner.
• Ensure the vehicle is parked on a level surface and the engine is cool before starting any repair work.

2. Replace Spark Plug and Ignition Coil

• Sub-steps:
  1. Disconnect the negative battery terminal to prevent electrical shorts.
  2. Remove the engine cover if applicable.
  3. Unscrew the ignition coil from cylinder 1 and disconnect the electrical connector.
  4. Remove the spark plug using a socket and ratchet.
  5. Inspect the old spark plug for wear; if it is fouled or damaged, replace it with a new one.
  6. Install the new spark plug to the manufacturer's recommended torque specification (typically around 13-16 lb-ft).
  7. Install the new ignition coil and reconnect the electrical connector.

3. Clean or Replace Fuel Injector

• Sub-steps:
  1. Remove the fuel rail to access the injector for cylinder 1.
  2. Disconnect the fuel line and electrical connector from the fuel injector.
  3. If cleaning, use a fuel injector cleaner and follow the product instructions. If replacing, remove the old injector and install a new one.
  4. Reattach the fuel rail and ensure all connections are secure.

4. Compression Test

• Sub-steps:
  1. Remove the spark plug from cylinder 1 for the compression test.
  2. Insert the compression tester into the spark plug hole.
  3. Crank the engine for a few seconds and note the compression reading; it should be within the manufacturer's specifications (around 180 psi is typical).
  4. If the reading is low, further investigation for potential internal engine issues is necessary.