Make sachets out of cut-up stockings and something called “Shake-Away Domestic Cat Repellent” (find it on the Internet), then tuck them away in convenient spots around the inside of the engine compartment. This product, which is scented with predator urine, does not give off an offensive odor but is very effective at scaring off most cats. The manufacturer even sells a “Stocking Ball Kit” that contains pre-cut stockings, measuring spoon, plastic gloves and instructions for making the sachet packets.