my Volkswagen Golf MK7 (2015-2019) has a rough idle when cold, what’s wrong?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.
• Ensure the engine is cool before starting work.

2. Inspect and Replace Spark Plugs

• Tools Required: Spark plug socket, torque wrench, ratchet, and extension.
• Remove the engine cover if necessary to access the spark plugs.
• Use the spark plug socket to remove the old spark plugs.
• Inspect the old plugs for wear; if they are fouled or worn, replace them with new ones.
• Torque the new spark plugs to the manufacturer’s specifications (typically around 22 ft-lbs for most plugs).

3. Clean Throttle Body

• Tools Required: Throttle body cleaner, soft cloth, and a screwdriver.
• Remove the air intake duct from the throttle body.
• Spray throttle body cleaner onto a soft cloth and wipe the inside of the throttle body, removing carbon buildup.
• Ensure that the throttle plate moves freely after cleaning.

4. Test and Replace Fuel Pressure Regulator (if needed)

• Tools Required: Fuel pressure gauge and basic hand tools.
• Connect the fuel pressure gauge to the fuel rail.
• Turn the ignition to the "ON" position without starting the engine and check the fuel pressure.
• Compare the reading with manufacturer specifications; if pressure is low, replace the fuel pressure regulator.

5. Check Engine Coolant Temperature Sensor

• Tools Required: Multimeter and basic hand tools.
• Locate the coolant temperature sensor and disconnect the electrical connector.
• Use a multimeter to check the resistance of the sensor; compare readings to specifications.
• If the sensor is faulty, replace it with a new one.