Now...we have bombs that go in your skull...we have grenades, why not car bombs?
Mind you, for balance, they'd have to expensive as hell...uber-difficult to install...we're talking explosives + auto-tech...at the very least. Plus I think it would only be fair if they had to be remotely detonated.
Also, I think it'd be fundamental that a card destroys most of the car parts but leaves the object around to be repaired.