Feedback when I start my car

I get feedback when the power inverter and FM modulator are on only when I start my car. The noise comes through all the speakers except sub. When I turn the modulator off and leave inverter on there is no feed back. when I play my cds or radio there is no feedback, when I turn my xbox on I get feedback while the car is running. Should I move the inverter some where else. Don't wanna move the FM modulator because the antenna wire isn't long so I don't have many options. Should I try powering my xbox from an extension cord in my house to see if in fact it's the FM modulator? I got the FM modulator grounded to my head unit I thought it might be the ground but I don't know. I tried other radio stations as well but no luck. Please help me thank you.

By the way the noise I get is like a whining that increases when I step on the gas. and when I don't push the gas I can still hear feedback.

You have some options. sound mech's refer this to nightmare ....I just saw nobody went to the plate. I don't like seeing someone hanging..so hear's SOME input. Did you install this system? The noise you hear is your coil..I'T's related to you're vehicles ingnition system . THIS CAN BE A TRICKY FELLOW SO DON'T TRY ANYTHING JUST YET...When it come's to12 volt ground's it can be down right annoying..you could have an amp grounded 15in away from a fuel pump and it will pick up humm..scoot it over 2in and it stop's You could allways try an isolator(have you heard of that?) I am very aganist that! If   you give me very detailed info. such as how much knowlege in 12 volt, dose it act different if you use the high beams...etc...is there any thing you can do to make it act different i've been(COIL NOISE FIXER) here alot let me know what kind of vehicle this is we can help you.(i mean i hope)=)

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