my Volkswagen Tiguan has a rough idle when stopped at a red light, what's wrong?

Solution

1. Preparation

• Gather tools: OBD-II scanner, socket set, multimeter, throttle body cleaner, vacuum gauge.
• Ensure the vehicle is on a flat surface and the engine is off before starting.

2. Clean Throttle Body

• Sub-steps:
  1. Disconnect the negative battery terminal to ensure safety.
  2. Remove the air intake duct connected to the throttle body.
  3. Use throttle body cleaner and a soft cloth to clean the throttle plate and surrounding areas.
  4. Reinstall the air intake duct and reconnect the battery terminal.

3. Replace Spark Plugs (if necessary)

• Sub-steps:
  1. Remove the engine cover if applicable.
  2. Disconnect the ignition coils from the spark plugs.
  3. Use a socket wrench to remove old spark plugs.
  4. Install new spark plugs, ensuring proper torque (typically around 15 ft-lbs; check manufacturer specifications).
  5. Reconnect the ignition coils and replace the engine cover.

4. Test and Replace IAC Valve (if necessary)

• Sub-steps:
  1. Locate the IAC valve (refer to the vehicle's service manual for exact location).
  2. Disconnect the electrical connector and remove the mounting screws.
  3. Replace with a new IAC valve if the old one is faulty (use a multimeter for testing).
  4. Reconnect the IAC valve and ensure all connections are secure.