Hello,
it seems, that action “Add a force to an object” (All objects → Displacement) is partially broken. Moving on X axis is OK, but on Y axis doesn’t move at all.
Really? Can you send me an example file showing the issue?
It is working for me 
Try to check the car position in the debugger (When you launch a preview, in scene tab ==> Debugger):
With the debugger ative, move the car with the key and check if the Y value changes 
Hm, my fault. My green ground is too big to define the move correctly. Thanks, Lizard-13, for the hint with debugger. Sorry for my false alarm.
