ZM2000:

Grounding aluminum foil is practically impossible. I used that statement to show that no matter what a wire is wrapped in it does no good unless one end of it is taken to ground, ie, the engine case, If left ungrounded the foil acts as an antenna and can collect static. If you don't believe me ask any ham operator that knows anything about antennas.
Think about your antenna cable on your TV. It has a shield on it that is grounded on both ends so that it can be used as a conductor for the tv signal. If one end is left ungrounded, it acts as a shield to take away all RFI that is picked up, so therefore your tv would not receive very good signal if at all.