Checking and replacing spark plugs (BMW X5 E53)

Checking and replacing spark plugs (SP) must be done in the following order. Turn off the engine and let it cool down to the ambient temperature. Check the condition of the new SP and their interelectrode distance. The gap can only be adjusted for two-electrode SP, by bending the base of the side electrode using a regulator with notches until the required gap is achieved.

• Check the condition of the porcelain insulator for cracks. Remove the ignition coils (IC) on a cooled engine, having previously marked them. Blow out the spark plug wells with compressed air; you can use a regular bicycle pump. It is recommended to replace the IIC sequentially. Unscrew the IIC with a special spark plug wrench, turning it counterclockwise.
• Compare the condition of the removed spark plug with standard options to assess the condition of the engine:
• the grey colour of the electrodes and the insulator of medium density indicates the normal operation of the spark plugs and the fuel mixture preparation system;
• the black color of the electrodes and insulator indicates that the mixture is too rich;
• light grey colour of the electrodes and insulator indicates that the mixture is too lean;
• oiling of the electrodes and insulator indicates that the spark plugs are working intermittently or there is increased wear on the piston rings.
• Check the spark plug insulator for traces of leakage currents, which are visible as thin random traces on the surface of the insulator. The cause of the traces is poor contact in the spark plug plug. Replace such a plug connection (PC).
• Apply a thin layer of anti-seize compound to the threaded portion of the new spark plugs, install the spark plug into the cylinder head holes and tighten it by hand until it stops. Using the spark plug wrench head and a torque wrench, tighten the spark plug to 25 Nm (2.5 kgf·m). Install the ignition short circuit in its place. Replace the remaining short circuits as described above.