So, I have a strange issue with my speakers. When my truck is sitting still, whether it be running or just on accessory, the speakers sound great. When I turn them up REALLY loud, there's a little bit of a buzz, but nothing bad at all. I put in drive and start going down the road, and I can barely turn it up enough to hear it and it's fuzzy and buzzing as though the speakers are blown. What could cause this? Fine when still, terrible when in motion. It's stumped me.

Thanks!

 

Is it a factory setup or do you have a custom head unit?

 

Factory unit.

 

That does make it interesting. I was gonna say if it was a aftermarket unit, that it sounded like it was a grounding issue. Has anything been installing that might have been tied into the same wires running the radio by chance?

 

Not by me. I have no idea what the previous owner might have done to it.

 

That sounds like a incorrect conection, either on the wiring or the player. Try giving some hits with your hand on top of the dash over the radio and see what happens. Do this when the car is stopped.
Also, ask somebody to listen all the speakers closely while you drive to find out if the noise is comming equal from all the speakers or just one.

 

I don't know if our trucks have RFI filtering caps but my car did and if those went bad you had some nasty static that came from the alternator and spark plugs.

if we do have some kind of RFI filters that could be your problem.

 

From my 2005 FSM

I think the first thing I would check is the grounds



SUPPRESSION COMPONENTS - RADIO NOISE
DESCRIPTION
Radio noise suppression devices are Installed on this vehicle. Radio Frequency Interference (RFI) and ElectroMagnetic
Interference (EMI) can be produced by any on-board or external source of electromagnetic energy. These electromagnetic
energy sources can radiate electromagnetic signals through the air, or conduct them through the vehicle
electrical system.
When the audio system converts RFI or EMI to an audible acoustic wave form, it is referred to as radio noise. This
undesirable radio noise is generally manifested in the form of “buzzing,” “hissing,” “popping,” “clicking,” “crackling,”
and/or “whirring” sounds. In most cases, RFI and EMI radio noise can be suppressed using a combination of vehicle
and component grounding, filtering and shielding techniques. This vehicle is equipped with factory-installed radio
noise suppression devices that were designed to minimize exposure to typical sources of RFI and EMI; thereby,
minimizing radio noise complaints.
Factory-installed radio noise suppression is accomplished primarily through circuitry or devices that are integral to
the factory-installed radios, audio power amplifiers and other on-board electrical components such as generators,
wiper motors, blower motors, and fuel pumps that have been found to be potential sources of RFI or EMI. External
radio noise suppression devices that are used on this vehicle to control RFI or EMI, and can be serviced, include
the following:
² Engine-to-body ground strap - This length of braided ground strap has an eyelet terminal connector crimped
to each end. One end is secured to the engine cylinder head(s). The other is secured to the plenum at the
exhaust heat shield forward/outer attaching stud.
² Resistor-type spark plugs - This type of spark plug has an internal resistor connected in series between the
spark plug terminal and the center electrode to help reduce the production of electromagnetic radiation that
can result in radio noise.
OPERATION
There are two common strategies that can be used to suppress Radio Frequency Interference (RFI) and Electro-
Magnetic Interference (EMI) radio noise. The first suppression strategy involves preventing the production of RFI
and EMI electromagnetic signals at their sources. The second suppression strategy involves preventing the reception
of RFI and EMI electromagnetic signals by the audio system components.
The use of braided ground straps in key locations is part of the RFI and EMI prevention strategy. These ground
straps ensure adequate ground paths, particularly for high current components such as many of those found in the
starting, charging, ignition, engine control and transmission control systems. An insufficient ground path for any of
8A - 82 AUDIO - SERVICE INFORMATION DR/DH
these high current components may result in radio noise caused by induced voltages created as the high current
seeks alternative ground paths through components or circuits intended for use by, or in close proximity to the audio
system components or circuits.
Preventing the reception of RFI and EMI is accomplished by ensuring that the audio system components are correctly
installed in the vehicle. Loose, corroded or improperly soldered wire harness connections, improperly routed
wiring and inadequate audio system component grounding can all contribute to the reception of RFI and EMI. A
properly grounded antenna body and radio chassis, as well as a shielded antenna coaxial cable with clean and tight
connections will each help reduce the potential for reception of RFI and EMI.

 

So, dumb this down for me... What do I need to do to try and fix this issue?

 

basically, start by checking the grounds on your truck, especially from the chasis to the engine.

To help, get the FSM for your truck, Weedahoe has it for free download.