Audio experts...please help!!

[Even Steven]

About 3 years ago, I installed an OEM Toyota navigation system into my 4Runner. The installation went perfectly and I've never had any problems at all.

So here's the problem: A few days ago while driving my 4Runner, I noticed that a lot of static started coming through the speaker system. I turned the head unit off and the noise continued to come through the speakers (keep in mind that the factory navigation headunit never powers off, even if it is turned off). The pitch of the static was consistent with my engine RPMs. I turned off my engine and the noise disappeared completely. Then I started the engine again, and the noise DID NOT come back.

The same scenario repeated itself about 4 or 5 times over the next week or so. The static just starts coming through the speakers, but disappears after the engine is turned off and then back on.

Other than the navigation head unit, my stereo system is completely stock. I did have to install a small amplifier, since the navigation head unit doesn't have a built-in amplifier. I'm starting to wonder if the small amplifier is bad, causing the static that I'm hearing in the speakers. I don't really think it's a wiring/grounding problem, because it goes away simply by shutting off the ignition and restarting the engine.

Anyone have any thoughts or suggestions?

 

[drmorbius]

It sounds like you have a spark leak somewhere. I would make sure all the clips to the spark plugs are tight. Also try looking around the coils in the dark and look for corona discharge. Hope this helps.

 

[Even Steven]

Okay, but then why would the static in the speakers come and go simply by shutting of the engine and starting it up again?

Wouldn't the problem remain constant if it had something to do with spark?

I'll check anyway, but I have very low miles on my 4Runner and nothing has every been taken apart under the hood. Do you think the problem could be related to the amp?

 

[drmorbius]

Okay why would the noise follow the engine revs? I take it the amp is older than the truck? If so it could be a bad capacitor filtering the 12v power in the amp. Also it could be a bad relay. Isn't there a tsb about the amps popping? Maybe this is related to that problem.
According to the schematic the relay is the acc cut relay . It shows normally closed.

 

[Even Steven]

Okay why would the noise follow the engine revs? I take it the amp is older than the truck? If so it could be a bad capacitor filtering the 12v power in the amp. Also it could be a bad relay. Isn't there a tsb about the amps popping? Maybe this is related to that problem.
According to the schematic the relay is the acc cut relay . It shows normally closed.

The static is definitely related to engine RPM, but even something as simple as a ground loop problem will cause RPM related static in an audio system.

My 4Runner is a 2004, and the amp was new when it was installed. It's not a big amp, just a tiny amp mounted up in the dash, below the head unit. The amp was needed because the navigation head unit doesn't have a built-in amp. Unfortunately, I don't know where the amp came from or what it was designed for, because it was included with the navigation system when I purchased it.

 

[drmorbius]

I'm running out of ideas. I don't understand why it resets when you cycle the key. Did you do the install, I mean could you take it back to whoever did?

 

[Even Steven]

I'm running out of ideas. I don't understand why it resets when you cycle the key. Did you do the install, I mean could you take it back to whoever did?

I installed everything. And everything worked perfectly for three years. Now all of a sudden, I'm getting this RPM-related noise through the speakers.

The installation was very straight forward. It was basically plug-n-play, without any type of custom work or wiring. I doubt the installation is a problem at all.

Why couldn't the amp be faulty? Could a faulty amp cause the problems I described earlier? It's the only thing that makes sense to me, especially considering that the problem will go away when I power down the amp by turning off the ignition. Maybe something internal in the amp is causing the problem, and turning it off and then on again temporarily "fixes" it.

What do you think?

 

[drmorbius]

I guess something could have become intermittent in the amp. It sounds like you have a feeling in that direction. Is it easy to get to? If so trade it out with another and see what develops.

 

[Even Steven]

No, it's not easy.... I'll have to pull everything apart to get to it. That's why I was wondering if it's even possible that a faulty amp could be causing the problem.

The reason I'm leaning that way is because nothing else makes sense to me. If I just changed my spark plugs and the noise started, I would probably be looking under the hood. But since this problem started out of the blue and for no apparent reason, I'm thinking that something went bad in the head unit or amplifier itself. And if the problem was consistent, I would probably be looking at the wiring, especially the grounding point.