The problem is not with the normals nor with the texture coords. There is currently a limit of WebGL where you can only reference 65k vertices per draw call, if you are using gl.DrawElements and the current implementation of the OBJMTLLoader does. So your car model (great model by the way) can not be viewed as is. You need to split it up. You can look in three.js/utils/converters/obj/split_obj.py. But there is an issue with the script, documented at https://github.com/mrdoob/three.js/issues/2397. So you will not be able to see the materials. So export many models from inside Maya or Blender and make sure that the resulting obj does not have a face index greater than 65535. Otherwise split again.
Also in the next release (three.js r59) I believe there will be a NormalHelper function so you will be able to view your normals.