In the GM underhood relay/fuse panel in general, there are also some small fuses, one of which relates to this problem. Pull some the smaller ones, like a red 10 watter, starting near the pump relay, and check the element. Also, it may be the fuse that blows if there is a problem (short circuit) where the plug goes into the AC compressor. If you find the blown fuse, and it blows again, check connection to AC compressor.
The fuel regulater diaphragm is bad, fix it.
if 4,6L Color is usually yellow or red egr - under manifold in rear O2 - rear back in axhaust manifold
My suggestion is to replace the IAC (Idle Air Control) or at least take it apart and clean it. MAny people have had problems with this part including myself. Idle acts irradicly high ,low ,wont idle . check it out and go to team3s.com for more advice and detailed answers
check spark plugs cap and rotor, and ignition coil. check gaps on spark plugs.checkfor blue fire getting through plug wires.ifso check egrvalve could be stuck open. check for intake manifold leaks. if egris good and no leaks are found check fuel pressure from pump. if fuel pump and filter are good check each injector for operation. they should open when interjized.