My 92 civic si engine starts to rev up and down when you come to a complete stop, the problem only occurs when the temperature gauge hits half. Not sure if its the heat sensor or something else.

Any help would be appreciated.

 

try iacv or the fast idle.

 

Or search for "idle surge".

Not all that uncommon, however, the cause usually is one of three things... IACV or FITV, as stated above, or a vacuum leak.

 

its the fast idle valve located under the throttle body take the cover off the back and screw the valve in a little it will fix the problem i have done this on a number of motors i have owned