Volkswagen Passat B8 (2015-2022) rough idle when stopped what's causing it

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is on a flat surface and securely parked.
• Disconnect the negative battery terminal to prevent electrical shorts.

2. Inspect and Replace Spark Plugs

• Remove the engine cover (if applicable) using a socket set.
• Disconnect electrical connectors from the ignition coils.
• Remove ignition coils and inspect the spark plugs for wear or damage.
• Replace worn spark plugs with new ones, ensuring proper torque (typically around 15 Nm).
• Reassemble components in reverse order.

3. Clean or Replace Fuel Injectors

• Locate the fuel rail and release fuel pressure using a fuel pressure gauge.
• Disconnect fuel lines and electrical connectors from the injectors.
• Remove injectors from the fuel rail and inspect them for clogs.
• Use a fuel injector cleaner or replace with new injectors if necessary.
• Reinstall injectors and ensure all connections are secure.

4. Throttle Body Cleaning

• Disconnect the throttle body electrical connector.
• Unbolt the throttle body from the intake manifold using a socket set.
• Clean the throttle body with an appropriate cleaner using a soft cloth to remove carbon deposits.
• Reinstall the throttle body and reconnect the electrical connections.

5. Vacuum Leak Inspection

• Visually inspect all vacuum hoses for cracks or disconnections.
• Use a smoke machine or carburetor cleaner around the intake manifold and hoses to check for leaks.
• Replace any damaged hoses or seals as necessary.