I have a Mach 1000 in an 04 gt. Lately (more times than not) when I turnthe stereo on, it'llwork fine 4 about 5-10 min.
then I'll get a reallyannoying buzzing like a bad ground. The funny thing is, to make it go away, I lean back really hard
in the drivers seat and the rear speakers make a loud pop and the buzzing goes away till the next time I have to turn the
stereo back on.
If anyone can help on how to fix this annoying problem I'd really appreciate it.

Don't know if it helps but everything in the car iselectric.

 

when you lean back it fixes it? sounds like we have our problem solved, stop leaning forward, you will have a better soundstage anyway........

all jokes aside this is the first I have heard of this. I agree that it is probably a bad ground(not sure what one "sounds" like after >10yrs installing) but I do not know why it would be related to the seating position. Which speakers make the noise? Woofer or tweeters? The tweeter amp is in the dash and might be loose.

 

Soundes like a loose amp wire...