my Volkswagen Tiguan has a rough idle at startup what could be wrong

Solution

1. Preparation

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

2. Inspect and Replace Spark Plugs

• Remove the ignition coils by unscrewing the retaining bolts and disconnecting the electrical connectors.
• Extract the spark plugs using a spark plug socket and ratchet. Inspect for wear or fouling.
• Replace old spark plugs with new ones, ensuring the proper gap is maintained.
• Reinstall the ignition coils and secure with bolts. Reconnect the electrical connectors.

3. Clean the Throttle Body

• Remove the air intake duct to access the throttle body.
• Using throttle body cleaner and a soft brush, carefully clean the throttle body and the intake manifold side.
• Reassemble the air intake duct securely.

4. Check and Repair Vacuum Leaks

• Inspect all vacuum lines and hoses; replace any that are cracked or damaged.
• Use a smoke machine or carburetor cleaner to detect any hidden leaks during idle.

5. Verify Fuel Pressure

• Attach a fuel pressure gauge to the fuel rail.
• Start the engine and observe the pressure reading; it should be within manufacturer specifications.
• If low, check the fuel pump and filter for issues and replace as necessary.