This guy does some amazing car models. he has a few Daniel Buck has tutorials on how to make parts of the car. not a whole tutorial from start to finish but good tips can be found in >>here<<
interesting fender. Sounds like you are asking for a tutorial for how to make a car, well the honest answer is that if you can box model a hand, or a head, or an arm you can box model a car. The technnique doesn't change, just the nunmber of operations.