Anyone have any ideas of how to deter mice from nesting on my engine block and munching on the plastic sleves for my wiring?

They have recently discovered my Tundra parked outdoors.

I let my dog mark my truck tire every so often. It seems to keep the mice and squirrels away.

Yea that would be marvelous if I had a dog.
I guess if I had a cat I’d have a sentry.

Not to sound satrical, perhaps I could get (buy) some fox urine (we use it in the frozen north to mask our smell)
when hunting large prey.

This happened to me when I used to park at my (now ex-) boyfriend’s house. (And, boy, is wiring expensive to fix!) My mechanic recommended putting D-Con under the hood and it seemed to work just fine, but I think breaking up with the boyfriend and parking back in my garage did the trick !!!

Actually that probably would work quite well. A mainstay of foxes’ diets are mice and other small rodents.

Some other tricks that people try are:
-fake owls nailed into a tree near the place where you park
-traps; I like the bucket traps:
-moth balls

Thanks for the additional information.
Fox mark is the choice.

Your state’s Department of Agriculture has experts in critter control. And their services are free.