Do you have the factory Mach Stereo? Or just the premium? It's possible you need a special harness adapter. Call Crutchfield, their by far the best people to deal with troubleshooting a problem. Now you know your vehicle has what is known as a din and a half size head unit. To install the bigger double din, your going to have to do some carving of dash. Couple of things you can check first. Keep the ground wires short, and hooked up to a solid clean ground spot. If using Rca cables to go to amps, keep them away from 12 volt power leads. Try moving balance and fader to all speakers, to isolate if it's maybe just one or 2 speakers. Same goes for separate amps. Disconnect each amp, to see if noise goes away. They make noise filters if all above fails. You can rule out any ignition or alternator as it does this without motor. Does it make the noise with radio, CD, or any input? Report back your progress.
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