vsv question

[Bru]

Hello
The (energized) power up VSV allows atmospheric pressure to the fuel pressure regulator at start up and for one minute after to give a higher fuel pressure than the vacuum regulated pressure. Helps to start faster idle smoother. Removing it or having one that is defective means that fuel pressure will always be regulated by manifold vacuum or pressure. This can be a problem for a heat soaked starting engine. A rough idle at start up due to vapor lock can result.

The (energized) EGR VSV also blocks off the vacuum and allows atmospheric pressure to the vacuum modulator of the EGR keeping it closed until the engine reaches operating temperatrue. Removing it or having one that is defective means that manifold vacuum will be applied to the vacuum modulator when the engine is cold. It can result in rough cold acceleration / running. Note that vacuum is not applied to the vacuum modulator at idle. The throttle has to crack open for it to operate. Otherwise the engine would stall.

Here is a helpful link about Toyota's EFI system including the 7MGTE engine.

http://www.autoshop101.com/forms/h22.pdf