Personally with this sort of thing I find it easiest to have a 'physics pivot' to keep track of all the forces on the car.
So to accelerate the car simply rotate the physpiv to the correct angle and apply a forward force. Each update move it towards the origin (I usually multiply the x,y and z coords by .9) this adds the friction.
Any external forces just translate the physpiv in the direction of the force.
Once you've added all external forces simply translate your main model by the x,y and z coords of the physpiv.
So to accelerate the car simply rotate the physpiv to the correct angle and apply a forward force. Each update move it towards the origin (I usually multiply the x,y and z coords by .9) this adds the friction.
Any external forces just translate the physpiv in the direction of the force.
Once you've added all external forces simply translate your main model by the x,y and z coords of the physpiv.