After reading lots threads from this forum, I successfully solved my idle issue after A/C turned on. I would like to share my experiences in return...

I have 95 4Runner 3VZE with unstable idle issue. Due to head gasket broken, I had replaced with a rebuilt engine about 10K miles ago. Not to mention I got this lemon car for only two months before HG broken.

After warm up, still difficult to adjust the idle screw to 750rpm. It is unstable and drifts between 1000~1400rpm when in park or natural. Put into gear either R or D, the idle speed will drop about 250rpm to 750rpm. It looks right but still drift up.

During the CA hot air, I have to turn on A/C. The idle speed will drop down to 450rpm while in D. It is about 300rpm difference.

I took the throttle body off and cleaned the Aux. air valve. Nothing wrong on the TB.

I took some pictures on the passenger side. Guess what I found? The vacuum hoses for A/C idle up valve and steering pump valve are all messed up! What a mechanic

Here are the pictures:
1) messed up hoses for steering pump valve - they all go to steering pump valve from the same Y adapter in the intake manifold.
2) messed up hoses for A/C idle up valve - they all go to A/C idle up valve from filtered air.
3) closed look of A/C idle up valve.

After exchanged hoses to the correct adapter, fired up engine, warm up, the idle is at 1100rpm. Now, I know that I overly adjusted the idle speed in order to compensate the power loss of A/C on. When the A/C is off, the idle speed bounced back to 1400rpm. When the A/C is on, the idle dropped to 1100rpm. When in gear, the idle is right at around 750rpm.

So, I turned on A/C to max. Re-adjust idle screw to 750rpm. Then, turned off A/C, still 750rpm. Turned on A/C, still 750.

Quite happy, right? NO!

When I put into R or D gear, the rpm dropped to 500rpm

Is it normal on dropping idle rpm when put into gear? Something wrong?

Thank you!

 

Are these photos posted the messed up hose order or the corrected order ? Having a hell of a time finding consistent vacuum diagrams for the PS and A/C idle routing

 

Don't mean to revive an older thread, but YES. The photos he originally posted are with the mixed up orders. The AC Idle lines should both be attached to the connections that come directly off the intake plenum. The PS Idle up lines go to the hardlines that run underneath the Intake.
Hope this helps you or possibly someone else as this caused me some headache before i figured it out



1992 3.0 Slow 4Runner

 

No, that's why we have an idle up valve to adjust it when needed. Maybe you have messed the vacuum hoses

For me this is the best diagram ever, enough you locate the hoses, "any diagram can help" , and conect them to the correct numbered places