Originally Posted by Drewski0523
It's a ground loop and from your description the rca plugs are picking up distortion. You can try grounding them directly. Also make sure they're plugged all the way in.
doesn't matter. still a ground loop.. and ground loops are not rca's picking up distortion(none of the wires are long enough for this to be the case), but multiple ground paths with different potential.
i would recommend moving the radio ground first(the metal radio brackets 'should' be ok, but there is a lot of plastic and bolts separating it from a real solid mounting point)-- there is a small metal box behind the radio with a 10mm bolt holding it down-- connect your radio ground to that bolt. that is a very solid metal support for the dash, so it should correct the issues.
also, what deck are you running? a pioneer perhaps?