i have read every post on idle and a/c problems on the forum but i cant find what i need. HELP

90 four runner 22re auto trans, on the valve cover there is a vacuum switch with a white electrical plug(2 wires) two small vacuum lines plug into this.
they go to a vacuum device on the intake manifold with a large black plastic screw and a spring under the head of it. also the vacuum lines from the power steering connect to this same device on the intake.
i am lost, my hanes manual dosnt list any of this and i dont even know what the stuff is called. my problem is that i dont get any idle up function at all.
when i turn the ac on it drops to 3-400 rpm. i am guessing that the white plug switches the vacuum around when the ac is turned on but i dont know how this circuit should function when it is working properly to compare to how it is now. this truck is new to me so i dont know how long it has been like this.
any help is greatly appreciated.

 

try turning the black plastic screw that you described. It controls the amount of vacuum to the ac switch. I cant remmber which way to turn it, but I THINK its clockwise. Maybee some else can confirm that.

 

oh, and welcome to yotatech

 

i forgot to mention that i get no change from turnig the black screw unless i remove it. then it stumbles and dies. tried it all the way in and 1/2 turn out at a time to recheck.

 

Hmm, well my knowledge of this is only limited by what I have come across in the past. Hopefully someone else can help you out.
Sorry I couldnt help out much

 

I think that valve on the valve cover is called a vacuum switching valve. It is supposed to keep the idle speed up while the air is on. It cycles on and off as needed. I know when my girlfriends went bad, the engine had a really strange idle when the air was on. Sometimes it would idle real high and sometimes it would stall out. That is about the extent of my knowledge based on experience. Hope it helps.

 

I have the same problem on my '89 Runner 22re!
My understanding is the black plastic screw is the idle up adjustment for both AC and the power steering.
The vacuum device on the intake manifold with a large black plastic screw and a spring under the head of it has a diaphragm in it. I can?t get enough pressure by sucking or blowing to get it to open, but with a toothpick it pops right open and lets the air flow. Does anyone know how to tell if it?s bad?