First off I have a 92 SI H23, Just got the motor rebuilt now im having troubles at idle it surges from abot 2grand down to 100 and dies when I come to stops. There are no cel's until I drive and hit about 4th gear and the it throws a code 23 Knock Sensor. Are the two related to each other, im not sure where to go from here. Any help would be great.

 

the knock sensor wouldnt give you idle problems. it could be a vacuum leak. did you do anything to your throttle body or get a new intake manifold or anything like that when you rebuilt your motor? oh, it could also be air in your coolant system. try bleeding coolant at the thermostat housing until you see a flow of coolant only (no air bubbles).