Its the IACV AKA fast idle valve. Its on the throttle body, take off the 2 phillips head screws in the round metal cover and you will see a plastic white peice with a slot on both sides and a little dome.Take a flat head screwdriver, screw it down and replace the cap. Its a vaccum leak and its freakin out the MAP sensor, thats why it goes up, almost dies and just drops back down. Good luck.