Sticky throttle

I'm a little new to working on fuel injected cars, as my regular car is a VW bug, but my wife has a 1989 323(noturbo)that has a sticky throttle. Let me see if I can explain the problem:
If the accelerator pedal is pushed in more than 1/2 way in, then the throttle sticks. When stuck, you can't pull the pedal back out with your foot. When I look at the linkage on the throttle body, it's rotated like the pedal is being pushed, but the cables are not tight like they would be if someone was stepping on the gas pedal.
I don't know what to do about this, as I have little experience with this problem. Can someone help? Has anyone else had this problem?
Thanks,
Nathan