Green’s Dictionary of Slang

shitcan n.2

[fig. use of shit n. (1a) + SE can]

(US) a near-derelict but just drivable second-hand car, or motor-bike, one step from the junkyard.

[US]L. Bangs in Psychotic Reactions (1988) 63: Blasting down the streets in a souped-up shitcan with some zit-grinnin buddies.