There is plenty of work for unskilled teenagers, but not cushy, easy jobs. All are going to be manual labor, working outdoors or working for low pay. You've got to decide what is more important, a nicer work environment (working indoors out of the sun) or working with something you enjoy (working on cars). If you can find a job that offers both, terrific! But decide on what is more appealing to you and go that way. People who like their jobs always do better at them, and always get the raises and promotions. So find something you like doing.
Since you like cars, here's a few ideas:
Lot Porter at a car dealership - Working outdoors, washing cars on the lot, almost every car dealership has porters doing clean up. Entry level job but you learn skills that can be used elsewhere, esp starting your own detailing business.
Jiffy Lube tech dude - Good advice already given, a job that's easy to get, people who like cars stand out here and are in position for promotions, if you are good with people even better, not the most fun or clean job but you are around cars all day. Don't forget the local oil change places and car dealerships, they need oil change dudes, too.
Car wash detailer - You can work on the line but see if you can get a job working in their detail center, most people who do this are immigrants but if you are good at it you can get promoted quickly, check out the local Turtle Wax car washes or any car wash that also offers waxing/detailing.
Parts runner for auto parts store - Requires clean driving record and pass a drug test, you drive parts to repair shops, other stores, etc. Most auto parts chains like Pep Boys, Autozone, NAPA, etc have small trucks that are used for deliveries. Gotta be good with paperwork and being organized.
Hope these ideas help. Good luck!