Now if i'm connecting 2AA batteries directly to the motor it pushes the car without any problem..
So without the arduino controlling the motors 3V will run the car on the ground or just freewheel?
i tried hooking it up to a stronger power supply because of the voltage drop but it didn't change anything either.
Stronger????? Higher current or higher voltage supply?
groundfungus is saying that with 2V of the 3V from the battery being dropped across the controller, your motor is only getting 1V to run.
You should try a 5V supply, this will have 2V drop on the controller and leave 3V for the motor.
To help we will need a circuit diagram and a photo of your project to debug and program problems.