You have slack in your throttle cable?... If you look underneath the drivers kick panel, at the top of the gas pedal, there should be a white bushing around the throttle cable and should be sitting in the slit in the metal. Is that bushing in the slot and is the cable tight?
Word I fixed this on my car. There's a bracket near the tb that the throttle cables bolt do. you just loosen both of the nuts and you can slide it and tighten it down. I think it tightens the cable when you pull it away from the tb. Don't tighten the cable too much or it'll start to open and give you a faster idle. It feels so much better without slack its so responsive.