Try harnessing the power of lightning, I hear there's a storm coming up in a few days.
If not, you can always hijack a train and push your car with it. Just be sure to never return to that time/location, or they'd hang you for theft.
edit: to correct Mark, it's 1.21 gigawatts
Try a lightening bold to channel the power into your flux capacitor. I hear it can generate 100 Gigawats
Im sure Iran or North Korea could help you out. By the way, do you know a Marty McFly?