why does my BMW 5 Series have a rough idle when I first start it

Solution

1. Preparation

• Gather tools and parts required for the repair.
• Disconnect the negative battery terminal to ensure safety.
• Allow the engine to cool down before proceeding.

2. Inspect and Replace Spark Plugs

• Sub-steps:
  1. Remove the ignition coils by unscrewing the bolts and gently pulling them out.
  2. Take out the old spark plugs using a spark plug socket.
  3. Inspect the old spark plugs for wear and gap them to manufacturer specifications.
  4. Install new spark plugs, ensuring to torque them to the manufacturer's specifications (usually around 15-20 lb-ft).
  5. Reinstall the ignition coils and secure them with bolts.

3. Clean the Throttle Body

• Sub-steps:
  1. Remove the air intake duct connected to the throttle body.
  2. Use throttle body cleaner and a soft cloth to clean the throttle plate and surrounding areas.
  3. Ensure the throttle plate moves freely without obstruction.
  4. Reconnect the air intake duct securely.

4. Check and Repair Vacuum Leaks

• Sub-steps:
  1. Inspect all vacuum hoses for cracks or disconnections.
  2. Replace any damaged vacuum hoses.
  3. Use a smoke machine or carburetor cleaner to identify hard-to-find leaks.

5. Fuel System Maintenance

• Sub-steps:
  1. Replace the fuel filter if it has not been changed recently.
  2. Inspect the fuel injectors for proper spray pattern and cleanliness.
  3. Use a fuel system cleaner if necessary to remove deposits.