motor noise

i jsut got ddone doing a sstem for a friend and i got it all done sounds good but whne the volumes down the subs wit there and pulsate or play liek the engine is running and its really loud if anyone could help me with this problem id appreciate it

heres the diagram of the car 

<<98 Mercury Mountaineer>>

"Sound"

Pioneer DEH7300

Pioneer 5/7 (4)

12'Kicker compvr (2)

900 Rockford Fosgate Amp (2)

what you go to do is check all of the wires for the head unit in the dash if there is a wire touching and metal in the car you will get feed back in the subs. i another thing you have to check is if a cd is loading up and you can hear it in reading the cd in the subs the rca jacks on the head unit are messed up and you need to get a new one. this just happened to me about a week ago

make sure u ran rca's separate from power and remote line also make sure if u grounded over a painted area u grind out that area and have a solid groundAudioPro111

A crappy amp will cause interference as well. In my case, the amp that powers my highs have horrible interference with the engine, but the amp for the lows does not. Seperate RCAs from power, check to make sure that the alternator on the car is in good condition, and check the amp (ie test the same setup but with a different amp). I'm trying to learn... trying.