I have the Mach 460 system in my '94 GT. This doesn't always happen, but several times per week when I start my car and the radio/cd player turns on there will be a background noise. It's not always noticeable at first. The weird thing is that if it's making the noise and I'm accelerating the noise will get higher pitched. If I'm decelerating it will get lower pitched. Anyone have any ideas what could be causing it? It makes the noise out of both lower door speakers. I'm not sure if it makes the noise out of the back speakers. Thanks in advance for your help.
I had the same problem with my 97 Contour. It was the ground wire if I remember correctly. But I had an aftermarket system, I don't know if this holds true for a Stock system.
Sounds like you have an alternator whine problem. Could be that the factory amps are going bad or you could have a bad ground. Either way the amps are picking up "engine noise". This even happens with aftermarket 4 channel amps, and it is usually a ground problem. Check that first, then go from there.
when i was at Ford, there was a TSB for replacing the cap and coil with a new design with brass contacts.
