The computer chips in cars are insulated, obviously, to keep the internal electrical system from burning them out. The basics for a Faraday cage are external metal frame, insulated from the ground and items to be protected insulated from the frame. The car frame performs the same function and four rubber tires insulate the car from the ground.
Most tactical military vehicles, aircraft, tactical generators, missiles, ICBMs, tactical computers and commo gear was shielded from EMP years ago.
Insulation means absolutely nothing to the currents/voltages induced by sufficient EMP.
That's what is known as a 'floating cage.' I have been inside flotaing- Faraday caged rooms where there were minute tears in the mesh. My radio and my cellphone both worked just fine until I located the breaks and repaired them.
It's the holes. The size of the holes that matters.
A car on a road in a lightning storm is most definitely *not* "insulated" from the ground.
That is pure myth. The only margin of safety a car body provides is that it *may* route the electrical current *around* you-through the steel body, suspension and eventually the wet tires to-Yup! Earth ground. Lightning has been known to strike car occupants through closed windows. Glass is a pretty good insulator-unless the potential difference is high enough for it not to matter.
The thing with cars and the like-remember the holes now...is that cars have some really *big* holes in them, you know, so you can see where you're going? It's why your cellphone works in the car. Now..while the actual semiconductor components (ECM circuitry) and the external sensors/solenoids are grounded and shielded by the fact that they are connected physically to the negative terminal of the battery through the car's frame and bodywork (which isn't always completely electrically bonded), the wires connecting these components arenot. They're hanging out in the open.
And what are inductors usually made from?
Wires that will carry an induced current to any and all of those highly sensitive microscopic semiconductor junctions-burning holes in them and destroying them instantly and permanently whether they're actually in a powered state or not. The EMP generates the 'power' that destroys them. Many semiconductors can be destroyed by the static electrical charge accumulated by your body under certain conditions.
Hence the ground straps that workers assembling/ testing components must wear to dissipate any stray static accumulations to protect the devices.
Mil spec vehicles designed to withstand EMP use completely shielded wiring harnesses and external components. Vehicles intended for civilian use usually do not.
The heavier and simpler the components-the more likely they are to survive EMP.
My old '66 VW bug would survive after maybe replacing a coil or condenser. It's also run on just about anything from vodka to cow whizz.