95 beretta 3100 woes

oh forgot to mention the milivolts were in the 250 ish range upons startup , then fell to around 100mv in open loop , and gradually dropped into the 90ish , to 50 ish and so forth , it actually hit 0 one time.

so im assuming its an 02 problem or circuit problem, ill end up picking up and 02 this week illl let u knwo how it goes