A decel dashpot or throttle opener is mounted to the throttle body on some engines. The decel dashpot is designed to keep the throttle valve from closing too suddenly during deceleration. The throttle opener is designed to hold the throttle valve open slightly after the engine is turned off.
Non ECU Controlled Throttle Opener Starting with 1990 3S-FE and 5S-FE engines, a simple throttle opener diaphragm was added to the throttle body. The throttle opener diaphragm is spring loaded in the extended position, holding the throttle valve open slightly when vacuum is not applied to the diaphragm. When the engine is started, manifold vacuum from the TO port retracts the throttle opener for normal curb idle.
The intent of the throttle opener system is to keep the throttle valve slightly open after the engine is turned off.
Non-ECU Controlled Dashpot On some engines, a simple dashpot is used. When the throttle is open, the dashpot diaphragm spring extends the control rod, allowing atmospheric pressure to enter the diaphragm chamber through a small bleed restriction (VTV).
• When the engine is stopped, spring tension extends the control rod, causing the throttle to open.
• When the engine is running above a given rpm, the ECU energizes the VSV, allowing atmospheric pressure to bleed into the throttle opener/dashpot diaphragm through the Vacuum Transmitting Valve (VTV). This allows spring tension to extend the control rod.
When the throttle closes, the throttle return spring pushes the dashpot control rod toward the retracted position. Atmospheric pressure trapped in the diaphragm chamber slowly bleeds through the restriction, causing the throttle to close slowly.
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