The same thing happened to my del sol si when i had it.....look right underneath the throttle body and you will find a regulator with a valve in it that is probably broken. It isabout the size of a deck of cards and held on by 3 10mm bolts and has a small hose connected to it.........i went and got one off of another sohc motor at a junkyard for $5...........lemme know if you have any questions