Auxilliary Port

[MR5H0LL]

Hoping someone can help me. I have a 2007 Ford Fiesta Ghia with a Aux port. When i connect my iPhone up to the stereo the sound is sometimes crackly and sometimes sounds like it is under water. When i change gear it either knocks the sound clear or crackly depending on how it already was. I thought it could be the cable at first but have tried 3 different ones and no change. Also tried hoovering the port in case it had some dirt. Any suggestions?

[Nico.]

if it is anything like the new fiesta the stereo cable runs near ish too the engine bay so picks up on that and you get a whining noise coming through the Speakers when nothing plugged in