Usually if you fold the exposed wire over the RCA shield (-) and plug it into the deck then attach the other end to the chassis it should work. If that's your problem.

 

if the unit is my problem, would it be both when the engine is running and when its not? because I only hear the noise when the engine is running and its going faster when i give some gas

 

does the wire have to be grounded on the car? because when I tried this i didn't put my unit back in the dash (to see if it worker). so the radio didn't touch to the metal bracket where it attaches.

 

Not necessarily, try running a different set of RCA's across your vehicle straight from radio to amp over/between the seats and see if that makes any diff. If the noise is still there, it's likely the deck. If the problem goes away, the noise is entering from the RCA's path somewhere. GL these problems are both annoying and hard to locate sometimes.

 

I had this type of ground loop and just left it alone. I realized that the chances of fixing it were slim.

 

If you have a pinched rca cable or a rca cable that is damaged it can also bring noise into the system. Yes the deck should have been back in the dash to check it. Again, there is absolutely no need to wire to all 4 connectors as shown in that pic (which looks like a dogs breakfast).

 

I agree it's a horrible pic, but it is the first one that google brings up and unfortunately I never took any pics of mine before I put it all back together. It does sound exactly like my problem though. What type of car did you say it was in?

 

acura rsx 2002