first 10% of throttle feels like a on/off switch

[a72510]

I have a 89 with a 5 speed and when I'm cruising along in traffic the first part of the throttle is like a switch, the car will try to buck when I let off and apply throttle.

It's like the TPS is screwed up on the first 10%

anyone have any ideas?

The idle also drops when I stop fast and kind of bounces from 300 to 600 rpm's and then settles at 900.

[sensibleS13driver]

I fixed my idle that had that exact same problem. there is a copper-looking screw/mixture needle (if you know what those look like) near the back of the intake manifold. mine was screwed in about 3 mm from flush, i backed it out to flush and now when i come to a stop it idles perfect an consistently at 900 with no dipping. it was very easy once you find the screw.