Horriable noise

I have done several installs in a variety of different cars, but this is driving me insane!

I have 2004 Grand Prix GT.  I have replaced the HU with a DUAL (not the best I know) 200.  I am running the highs off a 4 channel pioneer amp.  With the AMP using RCA plugs, no noise at all.  When using a portable CD Player to the 4 channel AMP, no noise.  When I hook the HU up to the amp, MAJOR engine noise.  When I hook up the speakers to the HU output, no noise.

• I've grounded the HU at the amp, no help
• I've tried 4 different RCA cables, no help
• I've ran a power wire dirrectly to the HU from the battery, no help
• I've regrounded the AMP, no help.
• Ive hooked up a test speaker at the amp, same noise.
• I've tried another amp (Rockford Fosgate 800a4), no help
• I've tried grounding the negative of the RCA to the chassis of the car, no help
• I've tried grounding the negative of the RCA to the chassis of the HU, no help
• I've tried another HU, no help.
• I've tried an isolated power supply to the HU, no help.

I've tried a ground loop isolator and that helped, but engine noise is still there.  So I tried all the above again with the ground loop isolator, no help.

I'm ready to give the car a viking burrial.  Any ideas?

I would think you have ruled out almost everything if you actually did all that you say you did!   I had that same problem in a customers gran prix a while back.  What I found is when he ran the rca cable, he smashed it behind the rear seat, seat back bolt, the noise dissapeared when we replaced the RCA's.  BUT,  you say you still have noise with two different HU's, two different amps, and 4 different patch cords.  That leaves the car or the install.

If the ground loop isolator helps quite a bit it is  probably a ground loop.  what the isolater does is basically disconnect the shield of the rca cables.

Hear is what I would try;

what happens when you unhook the antenna from th HU? (could be ground noise from there)

is the amp mounted to metal?  If it is, unscrew it and set it on a piece of wood, and try it again. 

unmount the radio, carry it to the trunk, wire it to the amp's power and ground plug in rca's try that. 

Does the noise change frequency when the engine rpm changes?

Are you battery terminals CLEAN and tight?

Did the factory system have an amplifier? and if it did, did you disconnect it?

do you have a ground wire from the negative terminal of the battery to the body of the car?

does the noise go away when the altenator is uplugged?

It could be a leaking diode in the voltage regulator in the altenator, but that is rare. 

good luck!

Thanks for the reply!

I should have added that unplugging the antena has no effect.  On a side not, my AM reception sucks too.  I'm not sure if its the head units faul or not.  When the car is off, the am reception increases though.

I havent unplugged the stock amp (if there is one, im not sure.).  I ran all the speaker wire directly from the amp to the speakers.  I had to cut and splice the terminals, though (because I am using the stock highs).

The battery is grounded (stock 8 guage?).  And there is no corrosion.  I very much dislike these types of battery terminals, though.

I'm at the point where I'm going to run a 2 guage ground back to the amps.  I have never had to do this before.  Is this a good idea or bad idea?  Thanks again for your help!

I have never had to run a ground wire to the battery on a basic install like this.

Lets get back to the basics,  did you use the class II databus interface that the car requires?  If you did not, and you hardwired the head unit, it may be that you are hooked to a data wire some how.  

If the factory system was a Monsoon system, there is am amp, probably in the trunk underneath the packing shelf.

I would be curious to hear what happens when you wire the entire system in the trunk. (I.E. the HU and amp all on the same ground and power wires.  You arent useing the decks speaker wires to run the amp are you?

He did this, and still had the problem.

I tried a Data bus II adapter at first.  I figured that my car requried it.  This is a long story.  When I first installed the Data Bus II, I had horriable noise with the ignition off!. Plus the "ding" from the door open was so ....... inconsistant is the only way I could describe it.  The first ding was fine and then it went down hill.  It was so laughabalel.  Ding... Diiiiiiiiiing, ding, dg. 

It was like the damn thing was dying.  I figured that it was defective and got a replacement.  Same problem.  I was convinced that my car needed it, though,  so I left it hooked up and i  was driving down the freeway at night then all the sudden all my guages went dead.  It scared the crap out of me and my friend.  So I pulled the Data Bus II.  I have since ran a power wire direct to the battery and my guages are working just fine for the last 2 weeks.

I just purchased a pioneer deh-6700mp and regrounded the amp to the tail light bolt (yes I've scraped all the grounds).  Same problem.  I am begining to think that this car is made of plastic.  I have tried 4 different grounding spots for the high amp, all with the same problem.  The deck is still grounded to the same spot via a 12 guage vire.

Well, I got sick of it and installed my 6 10'' Orion DVC subs hooked up to my Rockfor Fosgat 800a4.  Of course, the subs have the same horriable whine.

The lights don't dim at all and it hits hard, so I guess that I have a good ground?

I think my next step is to run another ground for the battery.

This is the worst install I have ever been a part of.  My love for this car has completly dissapeard.  What the hell is wrong!?

After the worst install of my life, I think I finally got the problem solved.

• I regrounded the battery with a 2 gauge strap.
• I braided the 3 pairs of RCA jacks together.  I read online that sometimes this helps.
• I ran the remote turn on down the same side of the car as the two other power cords (4 gauge and 8 gauge).
• I regrounded everything (again)
• I grounded the head unit to the stock wiring harness and ran a 12 gauge ground to the same place that my amps and crossover are grounded.

After all that, same noise.  So I started checking the stock fuses for the car.  I pulled the heated seats fuse as I don't have heated seats.  THE NOISE WAS CUT IN HALF.  So now I had just engine noise.  Not noise with the car off.

• Installed two ground loop isolators for the 4 channel amp.  Engine noise was almost gone.  just a little hum with the amp gain at 1/2.
• I installed a 20 watt isolated power supply for the amp.  ENGINE NOISE COMPLETELY GONE.  Even with the gain at 100%, no noise.  I guess the power wire is picking up interference in the engine compartment?

So I hooked up my EQ and crossover.  No noise at all.  I'm not sure if I still need the ground loop isolators or not.   I am just so happy that the noise is gone, I'm afraid to mess with it.

Sorry for the caps, but I am just so relieved.  I hope this helps someone else with a Pontiac who is having noise problems.