Help me diagnose my 6 months engine whine noise - diyAudio
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Old 23rd November 2016, 09:27 AM   #1
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Join Date: Nov 2016
Location: Irvine
Default Help me diagnose my 6 months engine whine noise

New register here, wonderful forum you guys got here. Just found about it and signed right up!

So as the title says, I have a Jeep wrangler that has been having really bad noise problems the past 6 months. I do know that there are hundred of threads about engine whine, and trust me I've read every one of those and I am still stranded. So I really need help with this thread to help me diagnose.

So I have two wranglers, a black one and a silver one. I did the sound system on the black one 3 years ago and it was perfect. I replicated the exact same sound system with very similar components in the silver jeep and I have unbelievable noise.

So I confirmed that the noise is NOT coming from the head unit. I disconnected all my RCA head-unit wires and the sound was still there. I did the same thing but from the amp side; I disconnected the wires from the Head unit to AMP and I still have noise. So when the AMP is powered without the inputs. I still have noise. At this moment I thought I had a bad AMP grounding, so I changed my amps ground and shortened the cable it as much as I can. No matter the location in the chassis, still I have noise. I checked the car's battery ground and it was connected nice and tight.

So I thought my AMP grounds are good. I must have a bad AMP! So I took the AMP from the black jeep (Exact same model and where the black jeep has no noise at all) and then I connected it to the silver jeep and I still have the exact same engine noise! Different amps didn't change anything.

So I thought it was a problem from the wiring from the amp to the speakers. So I disconnected all my speakers and I connected a stock jeep tweeter with a short wire extending out of the car. With only the stock tweeter in my hand outside the car I still had noise coming out from the tweeter! Even though the wiring I did to the mock up stock tweeter was literally a line from the amp directly outside the car. So there was no way that short wire would pick up any noise from the wiring. So now I ruled out the speakers and their wiring from amp to speakers..

The last test I did is that I thought I had a bad/weak alternator. So I borrowed the black jeep's alternator and I replaced the alternators. Same exact noise with different alternators. I also bought a BOSS ground loop insulator (B25B) and installed it from the amp to speakers, the noise was gone. But not only the noise, so is the whole sound. The sound quality now is raspy and clipped. I don't mind a little decrease in sound quality, but in my case when I installed the ground loop insulator the sound quality was so bad that it hurt my ears. Sounds like a 50s radio trying to pick up a signal..

So now I am properly confused. I could not cancel the noise in anyway possible! Its not from the head unit, nor it is from the amp, and it is not from the wiring. So what could it be? and A lot of people are telling just to lower the gains, but that will not work me at all, only gain setting were I can't here the noise is literally 0. And in that settings my speakers sound so quite I'd rather put the crappy stock jeep system back and it will sound better and louder than my new sound system.


Components on silver jeep (Car with noise):

Headunit: Pioneer AVH-4100NEX
Amplifier: Alpine PDX-V9
Subwoofer: Pioneer TS-SW2502S4
Front Speakers/tweeters: Focal PS165 speaker kit + tweeters and crossovers
Rear speakers: Alpine SPR-60 Coaxial Speakers
4.5 farad capacitor

The black jeep has the same amplifier, rear speakers, capacitor and the same model of the head unit just an older version of it. Front speakers and sub-woofers are different.
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Old 23rd November 2016, 09:52 AM   #2
oohms is offline oohms  Australia
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If you connect speakers straight to the head unit is there still noise?

Could be a problem with the 'big 3' wiring in the silver jeep
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Old 23rd November 2016, 11:24 AM   #3
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Location: Irvine
Quote:
Originally Posted by oohms View Post
If you connect speakers straight to the head unit is there still noise?

Could be a problem with the 'big 3' wiring in the silver jeep
I haven't tried that, good idea. Will do it now and see.

Big 3 wiring?
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Old 23rd November 2016, 12:32 PM   #4
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Join Date: Nov 2015
Location: Fife, Scotland
Ex service engineer - Guarantee jeep suppression at fault - don't know the jeep, but look to ignition if it's petrol, and any rotational parts in the electrics (you've tried the alternator.
If the whine is 'in tune' with the revving of the car, that points to anything driven - that could include the Air conditioning.
Refer to the car electrical diagram for any suppression provided by chokes or capacitors.
As soon as you swapped amps, it pointed in the car direction - next to that is the whine.
Dave.
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Old 23rd November 2016, 01:15 PM   #5
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You need a power line filter on the amps positive.
Install it at the battery after the fuse.
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Old 23rd November 2016, 07:39 PM   #6
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Location: Irvine
Quote:
Originally Posted by Old'n'Cranky View Post
You need a power line filter on the amps positive.
Install it at the battery after the fuse.
Will an inline power line filter decrease noise quality in any way? This is a big one for me if the noise quality got decreased. The ground loop isolators I bought were rubbish...

How do I pick an inline power filter? Is it between amp and battery or the battery and alternator. Could you recommend me any specific ones?
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Old 23rd November 2016, 07:42 PM   #7
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Join Date: Nov 2016
Location: Irvine
Quote:
Originally Posted by fastdave View Post
Ex service engineer - Guarantee jeep suppression at fault - don't know the jeep, but look to ignition if it's petrol, and any rotational parts in the electrics (you've tried the alternator.
If the whine is 'in tune' with the revving of the car, that points to anything driven - that could include the Air conditioning.
Refer to the car electrical diagram for any suppression provided by chokes or capacitors.
As soon as you swapped amps, it pointed in the car direction - next to that is the whine.
Dave.
Haven't full understood what you said, do you mind rephrasing? and yes you are right. The noise is in tune with the engine RPMs. More throttle = More noise.

If I disconnect the alternator, and I run the car without an alternator. There is actually no noise at all! but not sure how that info helps
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Old 23rd November 2016, 07:47 PM   #8
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Also I did one more extra thing today:

I've read that if my amp ground is not the same ground as the car's ground I will have noise. In my situation it is different, my amps ground is directly at the chassis under the seat. So I deleted that ground and extended a wire out of the car all the way to the battery "-" terminal. I was pretty sure that was my issue but it did NOT solve it. Huge bummer. The car and the AMP has the same ground, I removed power lines that were running near speaker wires and rewired them.

Everything checks out good but what could be my issue? Is my noise just incurable because of dirty power from alternator? I would hate to put a "band-aid" over the issue and not actually solve it. I would like to solve this issue without any filters if that is possible..
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Old 23rd November 2016, 08:06 PM   #9
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Location: Nottingham, NH
Probably need to power the amp through a common mode choke, also add some X and Y caps. You might be able to find a beefy enough one for free in a donor PC power supply. I don't know how much current your amp draws.

Click the image to open in full size.
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Old 23rd November 2016, 09:07 PM   #10
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Join Date: Nov 2003
Location: Louisiana
Can you clarify?

You stated that the amp produced noise with nothing but a tweeter connected to it.

Then you stated that the noise was gone when you used the GLI.

Did simply connecting the isolator kill the noise?

Have you tried installing the noisy amp in the quiet jeep?
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