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, which is typically provided by a fuel source like gasoline, diesel, or electricity. The energy released from burning these fuels is what propels the car forward.
Poop, on the other hand, is primarily composed of water, fiber, and waste products that don't have the capacity to generate significant energy or thrust. Even if we were to