Adjusting the CO content in exhaust gases (VW Passat B4)

This adjustment is performed on a warm engine, making sure that the engine exhaust tract is tight. Connect the gas analyzer to the measuring pipe of the exhaust system. Start the engine at idle speed. Check the CO content in the exhaust gases, which should be within 0.2-1.2%. If the CO content deviates from the norm, adjust it within the required limits, as indicated below.

Stop the engine. Disconnect the crankcase ventilation hose. Disconnect the vacuum hose going to the adsorber. Connect an ammeter in series with the electrohydraulic pressure regulator.

Turn on the ignition. Start the engine. Remove the plug of the fuel mixture quality adjusting screw located between the fuel metering distributor and the air flow meter. and using a hexagonal socket wrench for screws with an internal recess for a key, turn the adjusting screw so as to achieve an ammeter reading within 2-3 A.

Install a new plug on the mixture quality adjustment screw.

Warning: When adjusting the CO content, do not press the key or increase the crankshaft speed if the key is inserted into the screw head. After each adjustment, remove the adjusting key and briefly increase the crankshaft speed before reading the control current on the ammeter.