Idle mixture and speed adjustments are critical aspects of exhaust emission control. It is important that all tune-up instructions be carefully followed to ensure satisfactory engine performance and minimum exhaust pollution. The different combinations of emission systems application on the different engines have resulted in a great variety of tune-up specifications. See the Tune-Up Specifications at the beginning of this section. Beginning in 1968, all cars have a decal conspicuously placed in the engine compartment giving tune-up specifications.
When adjusting a carburetor with two idle mixture screws, adjust them alternately and evenly, unless otherwise stated.