why does my Volkswagen Golf MK7 (2015-2019) have a rough idle when cold

Solution

1. Preparation

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

2. Inspect and Replace Spark Plugs

• Sub-steps:
  1. Remove the ignition coil cover by unbolting it (if applicable).
  2. Disconnect the ignition coils from the spark plugs.
  3. Use a spark plug socket to remove the spark plugs.
  4. Inspect the old spark plugs for wear, carbon buildup, or damage.
  5. Install new spark plugs, ensuring the gap is set to manufacturer specifications (typically around 0.028-0.032 inches).
  6. Reattach the ignition coils and cover.

3. Check and Replace Coolant Temperature Sensor

• Sub-steps:
  1. Locate the coolant temperature sensor on the engine (usually near the thermostat housing).
  2. Disconnect the electrical connector from the sensor.
  3. Remove the sensor using a suitable socket (check torque values for reinstallation).
  4. Install the new sensor and reconnect the electrical connector.
  5. Refill any lost coolant and check for leaks.

4. Inspect and Clean Throttle Body

• Sub-steps:
  1. Remove the air intake duct connected to the throttle body.
  2. Use a throttle body cleaner and a soft cloth to clean the throttle plate and surrounding area.
  3. Reinstall the air intake duct securely.

5. Verify Fuel System Functionality

• Sub-steps:
  1. Connect a fuel pressure gauge to the fuel rail.
  2. Turn the ignition to the "ON" position (do not start) to check fuel pressure; it should be within manufacturer specifications (typically around 50-60 psi).
  3. If pressure is low, check the fuel pump and filter for proper operation.