Can I take my car back if I haven't finished making the down payment?

I live in Las Vegas, NV. I recently bought a used car and have had it for 2 weeks. I started noticing problems with it only after a week of purchase and had it checked out by a mechanic. The estimated cost of repairs was $730. When I took it to the dealership, they told me the gas cap was loose and that was the problem. Now there's an even bigger problem. The car sputters when accelerating as if it wants to stall out and the engine light flashes, meaning serious and dangerous problems with the engine. I informed the dealership, they said they'll fix it but have been evasive about any questions I've had continuously telling me to call back or come back another day. The car is under limited warranty, hasn't been registered yet, and I still owe $1000 dollars of the down payment. Basically, I'm done doing business with these people. If possible, how can I get the first part of my down payment back?