I say the idle screw because I had something similar happen on my silver truck that has the stock carb on it. It started idling high all of the sudden, and would rev up outrageously high till you had to turn off the truck. Adjust the idle screw after a couple of test drives worked for the fix. Not sure about the screw coming all the way out (I guess it could) but there is a good amount of adjustment that can be done.

88 Raider(Red):160k-Reman'd 2.6-5spd-Weber-SW Hubs-34x9.5 TSL-OffRd Pkg-1"Tbar-2"BL-CB
88 Raider(Silver):No 2.6/Bad KM145 Parts/Project
88 Montero(Brown):No 2.6,4.88s Parts/Project

[b]4X4 STICKERS,SHIRTS,ETC:
4WD Stickers AT COST.[b]