why does my BMW X3 F25 (2011-2018) have a rough idle when cold

Solution

1. Preparation

• Gather tools: OBD-II scanner, fuel pressure gauge, multimeter, socket set, torque wrench, and cleaning materials.
• Ensure the vehicle is in a well-ventilated area and parked on a flat surface.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Replace Air Filter

• Locate the air filter housing and remove the clips or screws securing it.
• Carefully take out the old air filter and inspect for dirt or blockages.
• Install a new air filter, ensuring it fits snugly.
• Re-secure the air filter housing.

3. Check and Replace Spark Plugs

• Remove the ignition coil harness and unscrew the ignition coils.
• Extract old spark plugs using a spark plug socket.
• Inspect the spark plugs for wear; replace them if they show signs of damage or excessive carbon buildup.
• Install new spark plugs and torque to the manufacturer's specifications (usually around 18-22 ft-lbs).
• Reattach the ignition coils and harness.

4. Clean Throttle Body

• Remove the throttle body from the intake manifold by unscrewing the mounting bolts.
• Use throttle body cleaner and a soft cloth to clean the interior, especially around the throttle plate.
• Ensure no cleaner residue enters the intake.
• Reinstall the throttle body and torque bolts to manufacturer specifications.

5. Replace Engine Coolant Temperature Sensor (if faulty)

• Locate the coolant temperature sensor, usually near the thermostat housing.
• Disconnect the electrical connector and unscrew the sensor.
• Install the new sensor, ensuring an appropriate seal.
• Reconnect the electrical connector.