[sammyg2]

Make darede sure your O2 sensor is hooked up and working, it is prolly old and tired.
Also inspect the wire connection to make sure it is in good shape and making good contact.
The system should adjust itself if it is warm enough.
Sometimes the O2 sensor doesn't get warm enough at idle to properly control the mixture, but at 15 and 25 mph it has no excuse. It is not doing it's job.

I installed a heated O2 sensor on my 80 SC and it works like a charm.