my BMW 3 Series G20/G21 (2019-2024) has a rough idle at stoplights, what's causing it?

Solution

1. Preparation

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

2. Addressing Ignition System

• Step 1: Remove the engine cover (if applicable) using a socket set.
• Step 2: Remove the ignition coils by unscrewing the retaining bolts and gently pulling them out.
• Step 3: Inspect and replace the spark plugs if they show signs of wear (gap should be set to manufacturer specifications).
• Step 4: Reinstall the ignition coils and secure them with bolts.

3. Cleaning the Throttle Body

• Step 1: Remove any air intake duct connected to the throttle body.
• Step 2: Spray throttle body cleaner into the throttle body while manually opening the throttle to clean both sides thoroughly.
• Step 3: Allow it to dry and reattach the air intake duct.

4. Vacuum Leak Inspection and Repair

• Step 1: Inspect all vacuum hoses for cracks or disconnections.
• Step 2: Replace any damaged hoses with OEM parts.
• Step 3: Recheck connections to ensure they are secure.

5. Final Checks

• Step 1: Reconnect the battery.
• Step 2: Start the engine and let it idle to check for improvements.
• Step 3: Test drive the vehicle to ensure the rough idle has been resolved.