The concept behind disabling vehicles ( or any form of electronics) works behind the idea of interfering with a system that uses pulses to operate ( like a digitally driven controller, you cars computer) as far as other components of a car like the starter or distributor, most of those systems run off flat 12v DC. DC operated systems are immune to such microwave interferance due to the fact that Microwaves (waves = AC = Alternating current ahh get it?) will totally put apperant "1"s and "0"s where there not suppost to be. In the case of DC, well, unless you can try to flip 650amps at 12v from a distance, your '69 GTO full of washed up rap stars on cocaine is safe.