If you find it hard to save you're probably just spending too much money on everything. If I can't manage to save much one month, it's typically because I blew too much money, not because random expenses popped up. Case in point, are both cars yours? If so, sell one, or both, depending on gas mileage/reliability/whether you have a car payment. 1 person doesn't need 2 cars!
If you're in the US, winter is several months away. I would save until then and then buy tires for whichever car you decide to keep. (See what I did there? I'm assuming you'll sell one because it's crazy for one person to have 2 cars!)