My Scanmaster acted strange too not long ago. I checked my connections and ran a new "'hot" wire" to an IGN slot in the fusebox. I have too seen all kinds of crazy knock while idling. I unplugged the orange ECM wire near the battery and re-plugged it in. All has been OK since. Fall down a well, eyes go crossed, get kicked in the head by a mule, they go straight again, I don't know...............