Throttle Opener Control System

When vehicle is first started, ECM activates a throttle opener Vacuum Switching Valve (VSV) which supplies vacuum to the throttle opener. The ECM controls VSV according to ignition signal, starter signal and signal from coolant temperature sensor. The VSV is activated when engine is cranking or engine speed is less than 4000 RPM for 2-35 seconds after engine starts.

When VSV is energized, this opens vacuum passage between VSV filter and throttle opener and closes manifold vacuum passage. When vacuum passage is closed, diaphragm spring pushes on throttle linkage, increasing throttle opening.

Once vehicle starts, ECM de-energizes the VSV, allowing manifold vacuum to pass through VSV to throttle opener diaphragm. Diaphragm will retract, allowing throttle linkage to return to normal base idle position.