There is a game called My Summer Car which lets you build a car from its constituent parts and race it.
And when I say "build a car," I mean it in the most boring way possible. You have to tighten individual screws, nuts, and bolts. and you have to use the right-sized tool for the job (picked a wrench that's one size too big? Sorry, fucko, get the right wrench!) When something breaks (and it will break), you have to pop the hood and examine the engine to find what's wrong (timing belt snapped, crankshaft broken, etc.) This can be incredibly inconvenient when you're in the racing portion of the game.
The reason such a genre is untapped is because, like real life, it is boring and frustrating.