Idle-Up Valve, Or is it Air Bypass valve????? Options

[Spider77]

OK. So ive been having this massive problem with my car when Im running the AC. While im driving its fine (save the the noticable loss of power). When I come to a stop, the whole care shakes like a nanny on a baby. So i did some reading about my "Idle-Up Valve" (or air bypass valve as toyodiy calls it). Why not take it out and do some resistance readings accross the terminals, they turn out to be fine, but I noticed this adjustment screw. I turned it all the way to the left (pass side), and turned the car on, ploped it in drive then turned on the air. Well, idle dropped to 200-250 ish, car almost wanted to die, but the air was still going. Went out and adjusted all the way to the other direction (driver side) and all of a sudden whe nI run my air, my idle dosent drop like it used to (used to do about 100 or so at stops. I used to press the gas a bit just to keep from vibrating so much).
My question would be does anyone have any info about the adjustment screw on this thing? It was marked at the halfway point, but I think all the way and back a bit it runs soooooo much better. I just dont want to jack anything up down the line by having it adjusted "too far".
Thanks

[azian_advanced]

how is your idle w/o the a/c running? it should be around 750 rpms when the engine is warm. turning the screw would alter your idle regardless if your a/c is running or not so it's not the best way to tackle the problem.

occasionally, i noticed with my car that when i stop while the a/c is running, the rpms would drop to about 250-500 and after about 4-5 seconds the idle up valve would kick in and raise the idle to about 900-1100 rpms.. so if yours isn't going up at all even after checking the wiring, it could be a vacuum problem or the valve itself. first check the hose between the idle up valve and the intake manifold/throttle body (whichever it's connected to). if it's ok, then try another idle up valve.

This post has been edited by azian_advanced: Aug 12, 2009 - 10:57 PM

[Spider77]

My car idles fine right now. As far as the idle being affected while the AC is not on (in regards to turning the screw), its not, untill the A/C comes on.

[Spider77]

[quote name='Spider77' date='Aug 13, 2009 - 5:52 AM' post='790294']
My car idles fine right now. As far as the idle being affected while the AC is not on (in regards to turning the screw), its not, untill the A/C comes on. I
even unplugged the valve and it didnt even affect the idle until i turned the ac on. So i know its tied into the ac system. If it shouldnt be adjusted why put the screw there? Just so im clear its the valve on the left side of the intake manifold under all those vac lines. Thamks

[Coligion]

My car used to struggle terribly while at idle and running the AC. It would drop from a smooth 800 RPMs to below 500 when the AC would kick in. This would continue everytime the AC would turn on and off. It basically trained me to never use the AC Anyway, I had to replace the IAC valve (not a cheap part) and now everytime the AC is turned on the valve immediately adjusts to the added stress on the engine and raises the RPMs appropriately.

This post has been edited by Coligion: Aug 13, 2009 - 3:33 PM

[Spider77]

What your describing pretty much sounds like what the idle up valve is supposed to do. Raise the idle when the AC is on. I cleaned out my IAC awhile ago when i was working on my TB, but I dont get how a new IAC raises the idle when the AC is on...Im gonna have to look into that.

[Coligion]

I tried cleaning out my IAC first before replacing it, but that did not solve the problem. It was simply no good anymore. the IAC valve works exactly as it sounds: it opens and closes when the engine load calls for more air to pass through and increase your RPMs (like when your AC is turned on).

This post has been edited by Coligion: Aug 13, 2009 - 8:36 PM

[Spider77]

Thanks for the replys, but I got a question here. In regards to vac lines, where can I source out a full set of new/slightly used vac lines (all the major ones at least) for a reasonable price?

[mikew04]

Some auto parts stores sell lines in different sizes by the foot. I think pep boys had them last time I went. Just measure and add together the lengths of all your lines then bring it home and cut to size. Shouldn't be too pricey.

[Spider77]

You know, I never thought of that. I didnt know if the lines had to be rated at something. Cause OEM they cost more than I think they are worth.