Soiled kitty litter, traps, even dryer sheets. Even bought a “ultrasonic” emitter off Amazon and wired to the battery. The varments took the dryer sheets and made a nest with them under the windshield cowl and probably slept to the “music” of the ultrasonic emitter! the best thing I’ve found is peppermint spray, I buy peppermint oil and dilute it in a spray bottle and wet entire under hood each week. also, I get the old timey toilet bowl deodorizer hangy things, put one in a sock and tie it up in the engine bay.