Sentra Wagon FWD L4-1597cc 1.6L SOHC (E16i) (1988)
AB-/BC VALVE CONTROL
When the idle switch is OFF, the I.S.C. valve opens in response to the amount of intake air and engine speed.
When the accelerator pedal is released, additional air is led into the intake manifold, actuating as AB- or BC valve.