I just replaced my throttle body on my 86 Civic SI. I had to replace it because my throttle angle sensor was missing and its not a replaceable part.
Anyways... I have hooked everything back up and it runs ok except after it warms up and the fast idle drops to normal it surges from 800 to about 1500 rpm. I have checked my vac hoses and they are all hooked up and look ok. I am wondering is this a symptom of a bad throttle angle sensor?? It didn't do it before I put the new throtte body on and my ECU code for it is gone now.

Any ideas??

Muddy

 

first re-set your ECU, then try it.. if not, re-set it again just to make sure and take off the IACV and start it up and set your idle.. then plug it back in and turn off the car

 

My car did the EXACT same thing--just loosen your throttle cable. It's your ECU fighting with your throttle cable to maintain idling RPMs. I was about to replace the ECU and TB, and my buddy just loosened the cable and voila; problem solved.