I diagnosed the same problem on a friends '84 a few months ago after 2 shops were unable to find the problem and replaced the ECU, O2 sensor, air flow meter, and a host of other parts. The shielded wire is to prevent spark plug noise, etc from entering the ECU through the sensor circuit. You will notice that the shield is only connected on the ECU end. If it were connected on both ends, the interference signal would be indused into the center conductor. I have not operated the ECU without shielding, so I don't know of any problems related to that. I replaced the wire, and it was a simple repair. I opened the ECU connector, removed the insulation around the shield and center conductors, and removed the wire. The shield is also connected to another wire, so I found it easier just to cut it off and solder the shield of the replacement along with the existing wire. The center conductor is on a terminal solo. I had some cable that was a good match...it is actually single conductor microphone cable. I just used a bit of it, and put a new insulated connector on the other end. I think Radio Shack has a single conductor shielded mic cable that would work fine. Just be sure that you don't leave any loose wires from the shield able to contact other terminals in the connector and the repair should be permanent. I would strip the end back, and put a piece of heat shrink tubing around the twisted-together shield. I'd then put a heat shrink "boot" around the area where the shield seperates from the cable. I'd then tie-wrap the new cable inside the connector to keep any stress from pulling the connection loose. Email if you have any question on this repair procedure, and I'll try to elaborate. Good luck. Steve Sandlin