recently installed system in my 2004 ford f-150 crew fx4 installed a pioneer avic 1 nav flip up head unit, 4 way pioneer 260 watt door speakers, 1- 10" pioneer 600 watt sub in a Q custom box under the rear seat. I powered the door speakers with a pioneer gm-6100f 600 watt 4 channel amp. I powered the sub with a pioneer gm- 5100t 760 watt 2 channel amp (bridged).

Here's my problem every once in a while the sub makes a continuous thumping sound not real loud but noticable, even if i turn the volume all the way down, or the radio off, the sound continues.

Does anybody know if this is caused from a bad ground, or any other thing that would cause this? any recomendations would ..............

 

A poor ground is the most COMMON issue with undesired noise. Get a star washer between the screw and body, let that washer dig it's teeth into the metal as you turn it down.

I have also seen too small of ground.

Damaged solder joints where the rca's connect to an amp(twisting and impacts).

Incorrectly run wires. By this I mean the audio cabling is too close in proximity to any high current wiring such as amp power, heater fan, ignition, etc...

L/O converters, amp chassis grounding(but you don't have this problem)

Poor deck grounding(but not common).

RCA's run backwards(some have little arrows)

Resistorless spark plugs - but that shouldn't be an issue anymore as well

My system started clicking/ thumping on its own one day, caused by a burned CD foil falling into the electronics of the deck.

I'm sure there's more, but maybe this'll keep you busy for a while

 

One of the most common problems there. Run the RCA's on one side, and the power and remote wire on the other side. Then if that doesn't do it, retry the ground. Or vice versa, the ground is probably easier to do first