A tachometer must be used to measure the engine idling speed. The connection scheme is different for different manufacturers, so you must follow the instructions given in the instructions for use of a particular tachometer.
Before adjusting the engine idle speed, first correctly adjust the valve clearances, the ignition system (advance angle, spark plugs) should work fine.
Warm up the engine to operating temperature and make sure the choke is fully open. Disconnect the radiator fan connector, turn off all non-essential power consumers and the air conditioner (if it is installed). On models with automatic transmission, set the selector lever to the position «N» and apply the parking brake.
Pic. 2.12. Location of quality adjustment screws (1) air-fuel mixture and speed (2) engine crankshaft
Start the engine and compare the tachometer readings at idle with those specified in the technical data. Adjustment is carried out by turning the screw for adjusting the speed of the engine crankshaft at idle (pic. 2.12).
To adjust the quality of the air-fuel mixture in idling mode, an exhaust gas analyzer is required (CO level meter).
Plug it in and let the engine idle. Compare the readings of the CO content in the exhaust gases with the value given in the technical data. Adjustment is carried out by turning the screw for adjusting the quality of the air-fuel mixture (see fig. 2.12).
If the air-fuel mixture adjustment screw is covered by a protective cover, remove the cover to access the screw.
If the composition of the fuel-air mixture in idle mode is adjusted correctly, re-check the engine crankshaft speed at idle and adjust it if necessary.
Stop the engine, disconnect the gas analyzer and connect the connector to the radiator fan.