To check if it's working you'll need to put a vacume pump to lower port of the diaphram(fast idle dia.)and adjust the speed,then make sure you actually have the a/c amplifier calling for (or giving voltage,12 v.) idle-up,w/a meter,test the connector at the vsv switch/solenoid,if you got both of those and still no idle-up then replace the vsv!
You can go to virtually any toyota car,truck or van (before 94' i think) at the junk-yard,and find the solenoid you need,I just replaced mine,it would work when cold and tested fine but when it got hot it wouldn't and bog the engine down like your's,I got four of them from all sorts of different models;camry,gts corolla,some tiny econo-box,even a van-you know the one with the "cab-over" look w/the long angled front end??? Paid three bucks from a "u-pull-it",Dealer wanted eighty bucks new!!! <img src="/forums/images/graemlins/nana.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> hope this helps,you'll need your a/c now!