EMP is a generic term that we tend to apply universally and always assume the worst with. EMP can come from many sources. I think what is being discussed above is EMP as the result of a nuclear blast. A side affect of said blast would be a huge electrical surge that can destroy most electronics, depending on many factors.... strength of surge, proximity to original source, quality of electronics, etc. Most preppers assume that newer cars, which are extensively controlled by electronics, will not survive the blast. The issue is not a short term suspension of electrical function, but an overload of electrical components causing enough damage to prevent continued function. That being said... you could buy older vehicles with fewer electronics... buy some spares and try to store them in a more protected manner, and then replace them once the pulse has passed. Theoretically, you would be up and driving again depending on your level of skill. This can even be done with newer cars if you can strip off all of the crap that was introduced by federal regulation. The motor and drive train should be fine.... it's all of the computer modules that would be affected.
So... I'd suggest a few days of research on the internet to learn everything you can... and maybe invest in a car without a computer... that you could get running quickly.
Keep in mind that in most cases where previous tests have shown EMP to be most effective... is right near a blast, or... further away when they were high altitude blasts. Longer distance effects were still noted... but not with the same significant amount of damage. I assume you will next ask whether we expect high or low altitude blasts. Well... that depends on what the bad guys are trying to accomplish. A High Altitude Blast (HAB) will knock out infrastructure over a larger distance... thus providing our enemy a place to invade and take over and re-start the infrastructure for their use. HABs minimize fallout as well. A Low Altitude Blast (LAB) will entirely destroy said target, will generate tons of fallout as the blast sucks up dirt and debris, but will minimize the EMP. Of course, if you survive a LAB, EMP is the least of your concern as you are probably being cooked alive from the inside.
One other thing... most nuclear-capable countries have experimented with EMP devices... bombs whose sole purpose is to knock out enemy capability without destroying the underlying infrastructure. If those types of weapons are deployed against us... you have two options... run and hide cause they are coming after you, but if they do... you'll be running and hiding the rest of your life... or try to organize the population towards defense of their property and hope you are ready in time.