I own a 1989 blazer v1500 and I have a problem when I plug my ALDL cable (Moates) my rpm rises from 600 rpm to about 1100 in park. When I drive around it stays High even when warm and if I park it then raises to 2000 rpm so it's anoying. It will do it regardless of the cable being plugged to the laptop or not. It does it with winALDL and tuner pro rt v5 so is there a ground or some other physical problem with the ALDL I should look for?

thanks Mat