Warm up the engine to operating temperature.
Turn on the high beam headlights (the electric fan of the cooling system should not work).
Bring the engine to idle speed, adjust the idle speed adjustment if necessary.
Adjustment of carbon monoxide (CO) content in exhaust gases
Measure the CO content in the exhaust gases at idle speed and, if necessary, adjust the screw located between the distributor and the air flow meter connecting air duct, after removing the plug.
Turning the screw clockwise increases the CO content, and vice versa.