Your mystery part is called an Idle Stop Solenoid. It's purpose is to hold the throttle blades at idle position while the car is running but slam them all the way shut when you turn off the key to resist dieseling. My 1970 Galaxie 500 rubbed through the insulation on that wire against the edge of the valve cover. Once in a while it would get in the right position to ground out, but never get a good enough connection to get a dead short. When it did that I'd get out of the gas and the engine would die.