If you can find the dead animal yourself, carefully remove it using gloves. Donning gloves again, scrub down all surfaces that had any contact with the dead creature with a commercial disinfectant or diluted bleach solution and let the car air out as much as possible. While Simmons says that dead animal calls are \"pretty rare,\" he's seen cases where rodents have climbed into the air conditioner's evaporator unit and gotten trapped, spreading the stench throughout the whole vehicle. You could try to sell it, but who's going to buy a car that wreaks of dead opossum? Not only could the dead animal result in physical damage to the engine, but its decomposing fumes might count as a biohazard.