Throttle Body: Description and Operation

In response to the depressing stroke of the throttle pedal, the throttle body opens/closes its valve to regulate the air volume to be taken in the combustion chamber.
During idling, the throttle valve is almost fully closed and the air flow through the throttle body is less than that passing through the carburetor.
More than half of the air necessary for idling is supplied to the intake manifold via the idle air control solenoid valve.
And the idle air control solenoid valve properly controls the engine idle speed, so it does not need to be adjusted.