I have a friend with a rebuilt throttle body (from a parts store). The shaft/blades move beautifully when the engine is off. With the engine running it gets sticky and sometimes won't close. Sometimes when he lets off the throttle the blades stick at like 10% TPS! Jabbing the pedal a few times will get it to close. Is this a failty rebuilt TBI? Or might I be able to help by adjusting the idle screw (aiming for ~10 IAC steps of course)?

 

Sounds like excess shaft play. Was the TBI body re-bushinged? When the car is running, the engine vacuum exerts a good deal of force on the throttle blades. This can cause the shaft to be pulled off-center if the TBI body is worn, which causes the butterflies to hang open.

 

With the engine off, the shaft seems tight as a drum...thats all I can really say. Gonna mess with the idle screw and see if we can't fix it. Idle IAC counts are too high anyway.

 

The best way to tell is to open the throttle by hand up 1/4 of the way and try to move the shaft side to side. Thats the best way to feel for excessive clearances. They usually feel tight when closed, but when you crack it open, sometimes the shaft can shimmy around a little if the clearances are off. The other possibility is that the new bushings aren't quite on center, leaving the throttle blades slightly mispositioned.