CEC System
DescriptionThe adaptive vacuum switch is closed during engine idle and partial throttle engine operation (adaptive mode of operation). The switch opens when manifold vacuum decreases to 9 inches Hg on vehicles equipped with automatic transmission and 13 inches Hg on vehicles equipped with manual transmission.
NOTE: In the adaptive mode, the mixture control solenoid is regulated to produce predetermined air/fuel ratios. During acceleration from idle speed to partial throttle and deceleration from partial throttle to idle speed, the oxygen sensor cannot react quick enough to the changes in the air/fuel mixture. As a result, high HC and CO emissions would be emitted momentarily unless the system switched the pre-determined programmed air/fuel mixture ratios.