Idles low and stalls out, but fine with a/c on....?

My friend has an 06 tacoma with the same engine as mine, a 2.7 4 banger, unfortunately he in not on tacomaworld so i am going to ask for him. his truck idles real low, like 500 rpm and lower, but when the a/c is on it runs fine. does anyone have any clue at all how i could help him?????

 

When the A/C is turned on a solonoid kicks up the idle linkage to compensate for the extra load of the compressor. I'm guessing his idle is set too low for normal driving. Back in the days of carbs, a simple idle screw determined where the throttle rested for idle. Not sure how its done now with the injection systems, perhaps similar. Open the hood and watch the throttle system at work while your friend blips the throttle in neutral. Perhaps it is simple enough to be 'cyphered' out by looking.