Like Fasteddy said,
I think you said that you loosened the idle screw. If so you do have to go thru the proper proceedure for the TPS/IS and the screw. You need the right feeler gauge and an analog ohmmeter. you probably know this already...
You might have a bad conection at the ECUs water temp sender

dave h.
'89 Raider V6 5spd;Aisin Hubs;; Gen2 LS: frt. brakes, rear coils;U.C.arms;R.trailing arms;idler arm; rear LSD axle w.disc brakes ;2 battery system for Dog's fan; relocated ECU; custom bumpers;J.Baker receiver;Conferr roofrack; t-bar crank.