See http://en.wikipedia.org/wiki/Contract#Remedies_for_breach_of_contract and http://en.wikipedia.org/wiki/Breach_of_contract
No .. you sign a sales contract which specifies the price and the contract which details the terms of the sale.. usually the contract is binding upon two conditions 1) the money being paid 2) the car being taken. Both of which are considered binding separately and indivisibly . i.e. if you take the car you are required to pay the money or if you take the money you are going to take the car.
So .. if condition 1 is not met then condition 2 cannot be met either.. i.e. if you don't actually have the car in hand you can't be expected to hand over the money. To be even less blunt .. you can't demand possession of something just because you have the money in hand to pay for it.
You seem to be confusing the creation (conclusion) of a contract with its performance.
Contract is created by offer and acceptance, whether in writing or orally. Performance/delivery is an entirely different issue. A good starting point to understand contract law might be the Sales of Goods Act of any Canadian province, which mostly codifies the common law.
Here is another great explanation of how contracts work (take from http://www.bbb.org/canada/legal-contracts-/)
The law of contracts is a vast subject area and is relevant to almost all areas of the law. A contract is an agreement between two or more parties which the courts may enforce. A binding contract must involve "offer and acceptance". They are legally binding once signed and cannot be cancelled unless there has been:
misrepresentation
fraud
duress
a clause that allows you to cancel
a mutual agreement to cancel