If you're driving an auto in D, does it matter? LOL
Until you can figure out whether the wire is damaged or shorted, I'd just as soon leave it disconnected to rule it out. The tach should never alter the behavior of the of the ignition - I have a tach, and my ignition does not fire at rest with the key on.
Hopefully your coil is OK, but I doubt it. Excessive current had a way of roasting electronics. It may work for now, but I definitely would drive cross town without a spare on hand!
