I mean, not that I did take it really seriously, but one question to ask with the symbolic nature of the car is: does it have any plot function, that the car is defect and that Vivian reacts to that (which is shown)? No it hasn't, as far as I can see. It is a superfluous info. So it must have a reason on a non-plot-level that the author gives us that info and scene. It could also be a means to show us more about Vivians character (angry reaction). But then why connecting that to the car? Because Hutch gifted it? This connection is objectively coincidental and has value, makes sense only on a symbolic level.
Of course one plot-function of the car defect could be to motivate the introduction of the mechanic. But that depends on how important he is going to be, and I would think also that there woud have been a more simple solution to that (she needs gas and stops at a gas station for example). It's a mixture of plot and symbolism: the mechanic is apart from his BBC a man who fixes something broken for her/ in her, something Hutch has left her with. It's like the porno plumber who is not merely a vulgar image but also a symbolic nexus of female sexual satisfaction and male problem solving skills in nonsexual areas. Vivian feels chronically unsafe because she distrusts Hutch's competence, which conincides with his sexual impotence.
