The plot synopsis as written on the DVD box refers to raccoons as "meddlesome rodents". Raccoons are not rodents and in fact are more closely related to bears.
Near the end of the movie, Jeff comes clean to Nealy. He does this in their car, idling while stopped. The car is a Toyota Prius hybrid, which would typically shut its engine off while stationary or at low speeds. Unless it was deliberately forced to keep running, the idling sound was added afterwards.