sleestak240

Hey all,
I'm trying to diagnose a small idle problem on my '87 4Runner. My suspicion is that it may be due to a vacuum leak somewhere in the power steering system. My truck idles decently at 800-850 RPMs but when I turn the wheel while idling I'm seeing a drop of 150-200 RPMs and a return to normal idle when I return to the starting position. Has anyone here seen this and successfully diagnosed and fixed it? A cursory investigation of the hoses coming from the power steering pump revealed nothing obviously wrong. Any ideas? Am I even on the right track?

curtiswyant

I don't much about the truck in question, but it seems to me that by turning the wheel at idle you're producing an extra load on the engine (driving the PS pump) which could cause the rpm to drop. As long as there's no noticeable performance problems, I'd say don't worry about it...

95RunnerSR5

my truck does the same thing as you sleestack its just another load on the engine... try sitting at a stop and pressing the break while turning the wheel and watch em drop

Willcipher

The power steering pump will place a noticeable load on the motor when you are turning the wheels from a dead stop. When the system is working properly, you shouldn't notice this at all. There is a pressure activated valve on the pump that should be attached to the upper plenum via two 1/4" hoses (assuming this is a 22RE). When significant hydraulic pressure in the system is present, the valve opens, allowing the intake air to bypass the throttle body by way of the diverter valve. The same system is used by the A/C to increase idle when the compressor is engaged. You need to inspect the two hoses from the PS pump to the upper plenum and adjust the white thumbscrew as needed. On a similar note, if the A/C compressor is reducing the RPMs at idle, you need to inspect the A/C VSV on the valve cover attached to the diverter valve.

^VooDoo^

Will is correct, If you still cant find the problem here are some Idea if its not bad vacuumlines.
The airvacuum valve on the back of you powersteeringpump is bad or you dont have one (Ive seen on some pumps, dont know why).
Also and this is a slap in the heard for those that Do the ISR mod and make the mistake of putting a plug or airfilter on the other end which connects to the stock ISR below the airfilter next to the radiator, (Its a 1/2 rubber hose)
This hose is the idle up for AC and powerstering and if youve done the ISR mod you need to connect this hose after the AFM and before the TB.

If you dont have the Valve on the PS you can add it and connect it to the spots marked here
https://www.yotatech.com/forums/show...hlight=plennum.