That's an... interesting question!
Unfortunately, it's not possible for a poop to propel a car. Poop is a biological waste product that doesn't have the physical properties or energy density to generate the force and motion needed to move a vehicle.
Cars require a significant amount of energy to move, typically provided by burning fossil fuels, electricity, or other forms of propulsion. The energy released from a poop would be negligible compared to what's required to power a car.
Additionally, the physical properties of poop wouldn't allow it to interact with the environment in a way that could generate motion. Poop is a soft, non-rigid substance