SUPER SIMPLE AND EASY FIX:
-go to radio shack and buy yourself a ground loop isolator. It will come with a 3.5mm end and a RF (red/white) on the other end. Since your car will have probably an AUX in which is also a 3.5mm, the RF (white/Red) cable will not fit in for obvious reasons. Radio Shack will also sell a ocnverter (black in color, probably an inch and a half big, hard black plastic converter that will couple the red/white cables to a 3.5 jack.
Should cost no more then 25 dollars and works like a charm!!!