why does my Toyota Highlander Fourth Generation (2020-present) have a rough idle at startup

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Clean Air Intake System

• Sub-steps:
  1. Remove the air filter housing using a socket set.
  2. Inspect the air filter for dirt and replace if necessary.
  3. Check the intake duct for cracks or loose connections and replace if needed.
  4. Clean the throttle body with throttle body cleaner and a soft cloth.

3. Replace Spark Plugs

• Sub-steps:
  1. Remove the ignition coil connectors and unscrew the ignition coils.
  2. Use a spark plug socket to remove the old spark plugs.
  3. Install new spark plugs, ensuring they are gapped correctly according to specifications (typically 0.043 inches).
  4. Reinstall the ignition coils and connectors.

4. Check and Replace Engine Oil

• Sub-steps:
  1. Remove the oil drain plug using a socket set and drain the old oil into a container.
  2. Replace the oil filter using an oil filter wrench.
  3. Reinstall the drain plug and refill the engine with fresh oil (refer to the owner’s manual for the correct type and amount).
  4. Start the engine and check for leaks.

5. Test and Replace Battery if Necessary

• Sub-steps:
  1. Use a multimeter to check the battery voltage; it should be around 12.6 volts when the engine is off.
  2. If the voltage is low, disconnect the battery and replace it with a new one.
  3. Reconnect the battery and ensure all connections are tight.