Carburetor idle speed adjustment screws
1 – mixture quantity screw; 2 – mixture composition (quality) screw
The engine idle speed adjustment elements include screw 2, which determines the mixture composition, and screw 1, which regulates the mixture quantity. To prevent the owner from violating the factory adjustment, plastic limiting bushings are pressed onto screws 1 and 2, allowing the screws to be turned only half a turn. If the bushings fail to adjust the CO content in the exhaust gases, then when unscrewing the screws, break the heads of the bushings, unscrew the screws, remove the bushings from them and screw the screws back into the carburetor.
Attention! The factory installs blue bushings, while service stations install red ones.
Adjust the idle speed on a warm engine (coolant temperature 90–95°C and oil temperature 75–90°C) with adjusted valve timing clearances and a correctly set ignition timing angle.
1. Using screw 1, set the crankshaft speed to 820–900 min⁻¹ on the stand tachometer.
The material is posted on the online resource: www.VAZbook.ru
2. Use screw 2 to achieve the concentration (reduced to 20°C and 1013 GPa (760 mm Hg.)) CO in exhaust gases within 0.5–1.2% at this position of screw 1.
3. Using screw 1, restore the crankshaft speed to 820–900 min⁻¹.
4. If necessary, use screw 2 to restore the CO concentration to 0.5–1.2%.
5. Press the plastic stop bushings onto the screws, aligning the bushing splines with the mounting lugs as shown in the figure.