What does this VSV do?
 

When I ground the wire on the temp switch (Circled in blue) the VSV (Circled in red) clicks. Question is, what does this VSV actually control?
https://cimg6.ibsrv.net/gimg/www.yot...d2dd958a51.jpg
https://cimg8.ibsrv.net/gimg/www.yot...533569d6e7.jpg

That's the vacuum solenoid valve. In a few words If it doesn't work right the idle will be errant.

For more details: https://www.toyotaguru.us/engine-con...sc-system.html

Yea, I know how it works but where does it hook to? I believe the other one in the lower left corner of the pic is the one your article is referring to. Or do they both just create the idle up? One (circled) temp related and one for extra load like lights etc? Not sure why I'd need extra air for either normal operating temp or low temp. (Depending on which way it operates. [normally open or normally closed] I haven't checked to see which it is.)

Check out page EC-19 in the link below.

https://cardiagn.com/emission-contro...86-89-4runner/

Cheers

This is what I was looking for! Thank you! This truck has had the reed valve removed so it is not needed.

Disagree!

The TSW (temperature switch) is what tells the ECU to toggles the FPU (fuel pressure up) wire to that VSV. It switch's the fuel pressure regulator's reference line between intake and atmosphere. I've covered this quite abit. It's an interesting and important part of the system.

I haven't checked exactly what that TSW does. It thought it is to shutdown AC when coolant gets too hot.
However, Like Co says, VSV either exposes fuel pressure diaphragm to atmosphere (higher fuel pressure) or to vacuum (lower FP)

All i can add is that I had to replace the VSV solenoid on my 3vze to fix some random idle surges I used to have. Per my understanding the VSV functionality is driven by Engine speed (Ne) Coolant temp, (THW) and Air conditioner clutch (A/C).

A VSV is a "vacuum switching valve", there are various configurations of outlets and colors and they all control different things.

When I ground the wire for that temp switch, that blue VSV clicks, so they're definitely related. I guess I could warm the engine up and find out at what temp that switch closes to be sure. I know there are (according to the wiring diagram in the Haynes manual) 2 temp switches. One I think was 30º C and one was 50º C. But again, who knows where each is located and if its even still there on this particular truck. I can definitely see the need for higher fuel pressure when it's cold and the CSI is running. According to the Haynes manual though it looks like the fuel pressure regulator is just plugged into that triple vacuum port on the back of the intake? I don't know. It's hard to follow because of the way they drew the picture.

You are referring to what the VSV controls,. I was referring to what controls the VSV. The 3vze has one VSV. and the solenoid opening/closing is triggered by the ECU based on the inputs it gets from Ne, THW, AC.

That is the idle up VSV you're talking about. Depending on the year, scope will correct me, there three more mounted on the right hand fender apron (AS, FPU, and EGR).

find one of the colored ones that match your model/build, your vacuum lines sound misrouted if it's not connected to the VSV.

My '94 has 6 VSVs. Two are for ADD and one is for A/C, so if your rig is a naturally-cooled rwd you probably don't have those. A/C is controlled by the A/C amplifier and the two ADD VSVs are controlled by the switch on the transfer case. The other three are for PAIR, FPR (or Fuel Pressure-Up) and EGR. Those last three are controlled by the ECM.

the CSI doesn’t really run like the other injectors. it is only spraying fuel when the key is in the start position and the intake air temperature is below a certain threshold. once the key is released to the “on” position, the CSI no longer sprays fuel, regardless of temperature.

The Fuel Pressure-Up is not for cold starts; just the opposite. It's to address vapor lock http://www.cygnusx1.net/Media/Supra/...taTech/h22.pdf (page 9), and activates after hot soak due to higher temperatures. Just so you know.

Oh OK. I just figured it would run until the engine got warmed up.

Good lord this thing runs so ass backwards from everything Ive had up to now. Batch fired injectors, higher fuel pressure at hot temps, etc etc.:con: