My idle drops badly (to around 500 rpm) when I turn on A/C on 3.0?
Where to look for faulty?
(A/C works fine, but mine TPS is disconnected because it's broken - maybe that's an issue?).

 

if the tps is unplugged it will not idle up w/ the a/c on. or it could be a bad vsv. for the a/c idle up..

 

There should be a vacuum valve which increases the idle when the a/c is on, it's located on the front inner pasenger side fender. I don't know exactly where as the 3.0 I had didn't have a/c. It also could be because of the disconnected tps, maybe the computer isn't getting the right information about the idle speed. Until you get that replaced you could try increasing the idle using the adjustment screw on the throttle body. If you set it about 200 higher than spec then it won't drop as low.

 

Check here for picts and where to make sure connected right.

If you have done the ISR mod, Sometime the Idle up hose is plugged up or a breather put on and cancels the idle up part.
The idle up hose is the one connected to the stock ISR below the airfilter and next to the radiator, about 1/2" dia, If the ISR mod was done then this hose needs be between the AFM and the TB for it to work right.
here is a pic to the AC idle up screw, Fig 4.
https://www.yotatech.com/forums/show...hlight=plennum

 

I don't have ISR mod - the only mod i have is disconnected tps.

So do i have to replace tps if it runs well with out it?