Re: what type of 'emp' device is used to disable motor vechiles.

If an **extremely** intense electric or magnetic field is applied to a 
car, it will cause large circulating currents in the car frame, body, and 
all wiring.  In older cars, this would disrupt the signals in the engine 
electrical wiring (very simple in older cars) and cause the spark to fail, 
causing the engine to stall.  In extreme cases, you could fry the wiring 
altogether.  In more modern cars (with computers) an EMP would kill the 
computer and thus disable the car.  Almost all military equipment is 
specifically designed to protect itself against EMP, for reasons discussed 
below.

As far as known devices for producing EMP, these are limited to 
specialized test fixtures, Tokamak fusion reactors, and nuclear weapons.  
That's why military electronics are hardened against EMP.  The effects on 
humans of nuclear weapons are well known, but the electronics must survive.