Here in Australia, we use the term "shitbox" (a slang) to refer to cars that are in bad condition, or just cars that are just bad.
Mate, my car's a shitbox. Barely gets to the local pub before she shits herself.
Before you flame me for profanity (if you even consider that word profanity in this day and age), here's a link to an official rally that is run here in Australia. http://www.shitboxrally.com.au/