I have a 1986 Ford ranger 2.3L ELECTRONIC FUEL INJECTION down on the passenger side near the passengers feet us a single wire with no insulation on it at all. It is ground to the inside of the frame, right beside the computer, it then runs through the firewall and out through the main wire harness but it's wrapped in a sort of aluminum sheeting with a blue and black wire, twisted together with it. When trying to find this particular wire in and the wiring diaphragms, this is one wire that i simply cannot locate. This wire halfway down my wiring harness has broken off and I'm just not sure exactly where this wire is actually suppose to go. Or is this wire the culprit of a single person, or did Ford actually put this in there themselves,? Please help!!

 

Its a Shield wire, no insulation/bare metal wire, it will only be grounded at one end, and really doesn't even need that

What shield wires are used for is to prevent RF(radio frequency) waves from interfering with low voltage signals that are passing thru the insulated wires the shield wire is wrapped around
Or to prevent the insulated signal wires from broadcasting RF and interfering with nearby wires
The bare metal wire acts like an antenna so dissipates any RF at the ends