Please Help???My sub has a Heartbeat WTF???

So I have a 2003 Mazda protege5 with factory HU and GromAudio Ipod adaptor with all stock speakers. I have built a custom fiberglass box and installed a 8" kicker comp sub to a Crunch Audio P500.2 amp.

The amp is under the drivers seat and the sub is placed on the drivers side in the trunk. Since I am using the factory HU I used the High-level inputs on the amp and spiced the wires into the rear speaker wires under the Drivers side door sill.
I have also grounded the amp and High-level input wire to the same spot, a bare metal(goldish looking) plate that holds the seatbelt mechanism under the Pilar between front and rear driver side doors. the Remote wire for the amp is run under the carpet and up to the back of the head unit spiced into a Pink wire that reads 12v in the Acc and on ingtion postions.

The power cable runs under the door sill over the fuse box and into the engine bay where it is hooked up to the + battery terminal with a large fuse about 6" from the battery. The speaker cable runs from the amp under the driverside rear sill plate to the sub in the trunk. I'm having a problem that when my car is running the sub seems to be moving (pulsing in and out slightly) and moves more when ever the engine fan kicks in.

It looks like the sub has a slight heart beat. What can I do to get rid of this problem. I don't want to get an aftermarket HU so that is out. Is it a problem with having the amp and high level input wires grounded tot he same spot? Am I getting noise thru the remote wire or power wire. The signal wire and power cable are only next to each other right near the amp. The power wire runs about 16" along the same line as the High level input wire till it turns towards the front of the car. Please give me some suggestions on what to change and how to fix this. Sorry for the long post just wanted to be throu. Thanks

 

I believe 4 ohm. It's a two-channel amp bridged. I believe it is about 200 watts RMS to the sub. Does that help?

 

So what would you do different with the Grounds? Is the problem because I have the amp and High-level input lead grounded to the same spot? I don't understand why i would have engine noise almost like the altinator noise coming thru a ground. what should I do?

 

well the sub doesn't whine or make any noise it just moves a little bit witht he idle of the car. I'll try switching grounding spots but I thought that the hardened metal would be a good spot.

 

so I moved my ground tonight and... No change!!! I sanded down a spot next to where the seat attaches to the floor in the unibody till it was nice and shiny and put a nut and bolt thru the gold plated ring terminal and bolted her down. No change, problem still exsists. Any other suggestions? I also tried to seperate the power and High level input wires more for like the foot that they run next to each other near the amp, that didn't help.

 

Set the gains by starting with them all the way down, turned radio up till about 80% then slowly turned the gain up till I heard distortion - less then half way - back off a bit and that was it. It's set to mon mode, with the the switch to the LPF mode HPF and LPF nobs are set at about half way with bass boost knob at about 25%. Is this wrong?

 

Also, I'm running RCA's has it's hooked up to the Factory HU. I'm using the High-level inputs on the amp hooked up to the rear speaker wires spliced in under the driver door sill.

 

So... Anyone else? would doing the big three help at all do you think? it only does it when the car is running and the HU is on. I tried to see if it did it with the Car running HU off doesn't do it. Car running high inputs removed doesn't do it. the amp stays on when the HU is turned off cuz of the remote lead I plugged into. Is there anyway that it;s a pblem with the amp? I just don't want to leave it and then have everything blow up on me in the future.