I live in a rural area and during the summer I park my XLE outside by my front porch, after a few days of not using it, I started it up and when I put it in drive the engine started to skip and idle very rough. It was so bad I shout it off and called my good old boy local garage guy.
He said to take the motor cover/soundproofing off and let him know how it looked, I found a two pound mouse nest tucked into the left top side of the engine, the mice pulled the soundproofing off from under the cover and made a nest from it, mixing it with dried grass, they also eat the spark plug wire cover from three plugs causing two wires to be eaten through.
The mechanic had to redo the wiring of the three plugs and told me to hang old soaks with moth balls on both sides of the engine compartment, which was done, since then no problems.
I found out wiring coverages made in the USA is an crude oil base and most wiring made outside of the USA is from soy oil and its eatable. Lesson learned look under the engine cover and dust it off. I now have moth balls hanging in my van, mower, generator and outside gas storage box, plus under and around all porch and patio things, I might smell like old grannies cloth closet, but I’m mice free now. Be careful using them around house pets.