ok when i start my car it idles i little higher to warm up like it should but when i drive for a while and the car warms up to regular operating temperature the check engine light comes on and when i get to a stop light or sign it idles either high or low like 1300-1500 or 500-600 sometime it still works fine. My car is a 1994 Honda Civic coupe with a b16 swap thanks for any help or suggestions

 

have you checked to see what trouble code you're getting?
how to chekc codes:
https://honda-tech.com/zerothread/1171263
find out and let us know.
Chris