how to diagnose rough idle issues in my BMW 5 Series G30/G31 (2017-2024)

Solution

1. Preparation

• Gather necessary tools and workspace.
• Disconnect the battery to prevent electrical shorts during repairs.
• Allow the engine to cool before starting work.

2. Replace Spark Plugs

• Remove the engine cover if applicable.
• Disconnect the ignition coils by unclipping the connectors.
• Unscrew and remove the old spark plugs using a spark plug socket.
• Inspect the old spark plugs for signs of wear or fouling.
• Install new spark plugs, ensuring the gap is set to the manufacturer’s specifications.
• Torque the spark plugs to the manufacturer’s specifications (usually around 20 Nm).

3. Clean or Replace the Idle Air Control Valve

• Locate the IAC valve (usually near the throttle body).
• Remove the electrical connector and unscrew the mounting bolts.
• Clean the IAC valve using throttle body cleaner and a soft brush or replace it if it is faulty.
• Reinstall the IAC valve and reconnect the electrical connector.

4. Inspect and Repair Vacuum Leaks

• Visually inspect all vacuum hoses for cracks or disconnections.
• Use a smoke machine to detect leaks around the intake manifold and vacuum lines.
• Replace any damaged hoses and re-check for vacuum integrity.

5. Check Fuel Injectors

• Connect a fuel pressure gauge to the fuel rail to check for proper fuel pressure.
• If pressure is low, inspect the fuel filter and pump.
• If necessary, clean the fuel injectors using a professional injector cleaning kit or replace them if they are faulty.