how to fix a misfire in my Toyota Highlander Third Generation (2014-2019) with code P0301?

Solution

1. Preparation

• Gather tools and parts: OBD-II scanner, socket set, torque wrench, compression tester, multimeter, and replacement parts (spark plugs, ignition coil, fuel injector, if necessary).
• Disconnect the negative battery terminal to ensure safety while working on the electrical components.

2. Inspect and Replace Spark Plug

• Remove Engine Cover (if applicable):
  • Use the socket set to remove bolts securing the engine cover and lift it off.
• Remove Spark Plug:
  • Locate the spark plug for cylinder 1 (refer to the vehicle’s manual for location).
  • Use the socket and ratchet to unscrew the spark plug.
• Inspect Spark Plug:
  • Check for signs of wear, fouling, or damage.
• Install New Spark Plug:
  • Gap the new spark plug according to manufacturer specifications.
  • Insert the spark plug and torque it to the manufacturer’s specs (typically around 13-16 lb-ft).

3. Inspect and Replace Ignition Coil

• Remove Ignition Coil:
  • Disconnect the electrical connector from the ignition coil.
  • Unscrew the bolts holding the ignition coil in place and remove it.
• Install New Ignition Coil:
  • Position the new ignition coil, secure it with bolts, and reconnect the electrical connector.

4. Check and Replace Fuel Injector (if necessary)

• Remove Fuel Injector:
  • Disconnect the fuel line and electrical connector from the injector.
  • Remove any retaining clips or bolts, and pull out the injector carefully.
• Install New Fuel Injector:
  • Lubricate the O-ring on the new fuel injector with clean engine oil and insert it into the rail.
  • Reattach the fuel line and connector.

5. Reassemble and Reconnect Battery

• Reinstall the engine cover and any components removed for access.
• Reconnect the negative battery terminal.