>
> not sure what you're gettting at in your first paragraph.
>

The tach is driven from the negative side of the coil.  So if the engine
stumbles or stops, quickly look at the tachometer.

If the tach needle drops like a stone instead of following the engine rpm
down, it means that your ignition primary circuit has failed.   Could be
ignition switch, 15-circuit wire to coil positive, coil, ignition driver
module on 1.9l, ECU on 2.1l, idle stab module on 1.9l, Hall effect sender
in the distributor or the connections to it.

Conversely, if the tach drops at the same rate the engine is slowing, that
means the ignition primary circuit is at least mostly ok, and you should be
looking at the high voltage side of the ignition or to the fuel
delivery/fuel injection system.  This of course is easier to tell with a
manual transmission, but you can still tell with an automatic.

Yrs,
d