But? You can't make an engine that goes forever? That's against all rules of physics! :O
Either friction, air resistance or... well, something, will always prevent it from going eventually.
Making an engine that can power itself might be possible, but not on planet earth anyway. I'm not very good at physics, but I know that you can't make an engine that produces more energy than what's put into it : )
Bread loaf goes in -> comes out as heat & poo