Pressure Distribution
 

I have a car solution and converged. i need to plot the pressure distribution vs distance (m) for the upper part of the car the upper stream only, i tried iso-surface but it doest allow me to chose the upper part it choses the whole car as one surface.

so you have pb with your grid
what s the type of your boundary conditions on the car (such a solid volume)
check if the car is created of multiple surface then use them to create dependent surfaces