There is no such economic theory as "Modern Monetary Theory". What goes under this name, are just a few assertions, one of them being that the banks can create credit without having deposits prior to. But this has long been known before and refers primarily to accounting rules in banks. To make things simple, just think that the deposits are already there in the Central Bank (since it can emit any required amount of money). And don't point to Federal Reserve, if you talk about creating money without a central bank, since Fed IS a central bank.

And I still don't understand your analogy with cars. Care to expand more on this more?