Algodoo

So i set up the engine a bit better and connected it to a wheel
to move the vehicle-thing, but it keeps getting screwed up.
even with the spring setting advice, it still gets messed up. i think it has something to do with mass
but i cant explain it. Someone please help me fix this so it works correctly.

[CONTROLS]
{SHIFT+I to START}
{Y+U ENGINE BREAK (TOGGLE)}
{UP= LOCK ACCELERATOR}
{DOWN= BREAKS}