how to keep mice out of my cars engine bay?! i've tried everything!?

so.. i've gone through a lot of trouble with mice getting into my car. so far they've done only $200 worth of damage - but they keep coming back for more no matter what i do.

they never get in the actual car, just crawl around the engine bay. my car sits in a carport that is absolutely NOT mouseproof and most likely never will be. I put 20 or more mothballs in the carport so my whole carport wreaks. i also saw online to put cut up bars of soap around the car.. put 3 bars of soap under the engine bay, in the car, and all around the perimiter of the carport. and lastly i have 5 mousetraps loaded with cheese placed around the car, by the front tires, and around the perimiter of the carport. oh and ps: they are not getting cought in the traps, and the mothballs dont work because i put some in the engine bay and they pooped on them...

Besides all of this i KNOW mice are still getting in my engine bay because i always find a bunch of mouse poop and chewed up acorn bits and lots of other miscellaneous mouse particles.

PLEASE PLEASE help. i want to get rid of them before i have a big big big bill on my hands.

ALSO: do not reccomend mouse poison or anything that would kill them (unless it kills them instantly - like traps) because then the mice will eat the poison - crawl into my car's vents and die.. theres your repair bill right there.