my Honda Accord has a rough idle at stoplights, what could be causing it?

Solution

1. Preparation

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

2. Inspect and Replace Spark Plugs

• Tools Required: Socket set, spark plug socket, torque wrench.
• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the ignition coil connectors.
  3. Remove the bolts securing the ignition coils and pull them out.
  4. Use a spark plug socket to remove the old spark plugs.
  5. Inspect and gap the new spark plugs as per manufacturer specifications.
  6. Install the new spark plugs and torque them to the recommended specification (typically 13-20 lb-ft).
  7. Reinstall the ignition coils and connectors.

3. Clean or Replace the IAC Valve

• Tools Required: Screwdriver set, cleaning solvent, or replacement IAC valve.
• Sub-steps:
  1. Locate the idle air control valve (refer to the service manual for location).
  2. Disconnect the electrical connector from the IAC valve.
  3. Remove the mounting screws and take out the IAC valve.
  4. Clean the valve and its port with a suitable cleaner or replace it if it’s faulty.
  5. Reinstall the IAC valve and reconnect the electrical connector.

4. Inspect Vacuum Lines

• Tools Required: None specifically, but a flashlight may help.
• Sub-steps:
  1. Visually inspect all vacuum hoses for cracks, leaks, or disconnections.
  2. Replace any damaged hoses with new ones.
  3. Ensure all connections are tight and secure.

5. Fuel System Check

• Tools Required: Fuel pressure gauge.
• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position (without starting) and check the pressure.
  3. Compare reading with specifications in the service manual.
  4. If pressure is low, inspect the fuel pump and filter for issues.