There is a whole guide to troubleshooting noise here: Induced noise/Ground loop trouble shooting guide.
I have a cheap Lightning Audio(from Wal-mart) amp that for some reason makes a high pitched noise in the speakers that is from the engine. I know its cheap, but i had it hooked up in my old car and it didnt do this. It may be my wiring job, im a novice at it. I bought a noise suppressor form wal-mart, but it cut out parts of the music along with the noise. Most people i talk to tell me its a ground problem, but i put it under the large bolt that holds the seat in the car, so i dont believe its the problem. I called the number on the back of the noise supressor box, and they said that it could be that i ran all the wires on one side of the truck, but i seperated them and it made no difference. Does anyone know what would cause this?
redo your ground whether you wanna belive it or not you prolly have a bad ground make sure there isnt any paint where you grounded at
Check your grounds
chk u wires and used high Qaulity