Thank you for replying ..
i tried your suggestion, but it did not work because there are phys applied to the car.
here, i read something in phys FAQ:
Q: How do I move a physics entity ?
A: Apply a velocity, force or torque to it. If you have set up a constraint on the object, you can also use the phcon_setmotor function to set its movement. Don't attempt to change its position or orientation directly by altering his x,y,z coordinates or angles, or by c_move or c_rotate - this won't work for physics entities.
i tried using 'phcon_' but did not succeed..
hope that someone can help me.