It is probably a loose wire on the distributor pickup. I am not totally
familiar with the mustang tach system but had a similar problem with a
Fiero. the wire was actually burned through and would short out.
<landsteam.TakeThisOut@yahoo.com> wrote in message
news:1169153370.961063.231690@v45g2000cwv.googlegroups.com...
> What would cause the tach to go to zero with the engine still running
> then go all the way up and down. It's not in tune with the actual rpm
> of the engine. Is this a expensive problem?
>
>> Stay informed about: 96 cobra tach going crazy