1997 Montero Sport engine noise

I installed a sony cd player in this vehicle and there is a little engine noise coming through the radio when the engine is on.  The cd player is clear as a bell.  There is no noise when the engine is off.   I have run a new ground wire to the passanger kick.  I have even tried a isolation trasnformer from Radio Shack.  Nothing seems to help.  Is there somthing that I am missing?  I have even seperated the power wires from the speaker wires at the back of the unit.  Any help to get rid of this noise will be much appreciated.  Thanks in advance.  Brian

It is likely that it is not alternator noise, but it really IS engine noise.  Most likely it is coming from your spark plugs or spark plug wires.  How old are these items?  Try replacing the wires, and/or replacing the plugs with resistor types.  Do not skimp on the wires, especially, USE THE OEM ONES!  I have always had good luck with ND or NGK plugs, and they are most likely the recommended plug for your Mitsu.  Avoid Champion and ACDelco, I have almost always had bad luck with them.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Thanks for the info.  I will give it a try.  Brian