That wire is not getting any extra current, you just have a bad wire.
Current takes the path of least resistance to ground. In your situation the spark plug wire either, has cracks in it, a break in the core, or bad connections to the end connectors. What you are hearing is the current jumping to ground through the insulation, or across a break in the wire.
If you open the hood at night, or in a darker area, like the garage, you might be able to see this spark. Sometimes a really bad spark plug can cause this, but my first guess is the wire.
The solution would be to get some new spark plugs wires.
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Current:
2007 Dodge Sprinter
2003 Toyota Sequoia
1994 E150 4X4
1955 F250
Gone but not forgotten:
2006 Toyota Tacoma Quadcab 4X4
1999 F250 4x4 Super Duty 7.3L Powerstroke Diesel
1998 BMW M3
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