In Mexico, mostly in the North, obviously influenced by the USA expression, many people say "un limón" for a used old car that won't actually work.
We don't really have a word equivalent to "batata", but we use a lot "porquería" or "mugre" for something we bought expecting a performance that is far better than the one we get.
- El carro me salió una porquería. Me deja tirada en la calle a cada rato.
- Este teléfono es una mugre. La batería no le dura nada.
@Poli: "Mosquita muerta" is only used for people, because they have an intention to deceive. Objects do not have this intention.
