what could cause my Volkswagen Golf MK7 (2015-2019) to have a rough idle when cold?

Solution

1. Preparation

• Gather necessary tools and parts.
• Disconnect the battery to ensure safety while working on the electrical systems.

2. Inspect and Replace Spark Plugs

• Remove the engine cover if applicable.
• Use a socket set to remove the spark plug wires or coils.
• Extract the spark plugs using a spark plug socket.
  • Tools Required: Spark plug socket, ratchet, torque wrench.
• Inspect the spark plugs for fouling or wear; replace with OEM equivalent if necessary.
• Reinstall the spark plugs and reconnect the ignition components, ensuring proper torque (typically 15-20 Nm).

3. Clean or Replace Idle Air Control Valve

• Locate the IAC valve on the throttle body.
• Disconnect electrical connector and remove mounting screws using a socket set.
• Clean the valve with throttle body cleaner or replace if damaged.
• Reinstall the IAC valve and reconnect the electrical connector.

4. Inspect and Clean Throttle Body

• Remove the air intake duct to access the throttle body.
• Use throttle body cleaner and a soft brush to clean the throttle plate and surrounding areas.
• Reassemble the intake duct securely.

5. Verify Coolant Temperature Sensor

• Locate the coolant temperature sensor; disconnect the electrical connector.
• Use a multimeter to check for proper resistance according to specifications.
• Replace the sensor if it is out of specification.