EMP(Electromagnetic Pulse) strikes disabling car computers is a Myth, the studies done on this placed it at MAYBE 1 in 50, and it depended on the wiring and materials in the vehicles, assuming all vehicles were same distance from EMP
It wouldn't effect any vehicle computer that were farther away, running or not
EMPs can disable power grids because they are exposed, and can act as giant antennas to send EMP to homes and offices
These act similar to lightning strikes, so unplug it and its safer
There were a few companies trying to get police a way to stop a vehicle via an RF pulse, not sure if any got them to work
Might be able to overload the coil, which would work on any spark plug engine regardless of year
I know attacking the electronics is the popular theory, but more suited to handheald and home/office electrionics, vehicle electronics is much simpler and surrounded by metal, a Faraday cage