What Does the Throttle Valve Do

In a conventional gasoline engine, a throttle valve is used in the intake manifold to reduce the power output for part-load operation. Varying the throttle position (TP) controls the amount of mixture (air + fuel) inside the engine, while the AFR is kept constant.

What will happen if the throttle valve open?

The main fuel jet comes into action when the throttle valve is further open. Then the venturi-shaped air-flow restriction creates a reduced pressure for drawing fuel from the main jet into the air stream at a rate related to the air flow so that a nearly constant fuel-air ratio is obtained.

Can a bad throttle body cause a car to shut off?

When a throttle body is not functioning correctly, some noticeable characteristics may be poor or very low idle. This can include stalling when coming to a stop or very low idle after starting, or even stalling if the throttle is quickly pressed — resulting in the throttle body plate opening and closing very quickly.