Engine Noise.

[alexj01_83 6]

I'd put a dollar on a hundred its your rca's. I had a set of those and a bad case of alt noise. they look similar to the ones I had gotten from radio shack, they weren't shielded good enough. My first remedy was to get a set of in-line filters for my rca's. That worked well. Then i bought a better set, and it took care of the noise all together.