01 XJ Radio Interference

[JMA_2001XJ]

So today out of nowhere I was driving and started to get a random crackle in all 4 speakers. It does not change with throttle input and is sporadic but constant. When the car is parked and the key in ACC or IGN it is fine and there is absolutely nothing wrong, no crackle. As soon as I turn the ignition on and the XJ is running it starts. It does not matter what source I am listening to.

It is an aftermarket Power Acoustic headunit that has been working perfectly fine until today. I pulled it out of the dash to check all the wiring but that seems to be in order. Moving the wires around does not affect the crackling.
I had another radio on hand and checked it with that one and it is doing the same thing, so I am guessing that I can eliminate a faulty headunit. There is no external amp or sub of any kind.

There is a vacuum leak that I have narrowed down (with a smoke test) to the throttle body butterfly shaft that has been causing a horrible high pitched noise on deceleration and possibly causing an occasional misfire in cylinder 3 and CEL that clears with a code reader. It only comes one rarely, I just drove for hours yesterday and there was not an issue. After the crackling started today I stopped at a store, came back to the XJ and when I started it the CEL came one for the same misfire and cleared and has not come back on but the crackling persists.

I would think that if it was an electrical issue it would have some correlation to throttle input which it does not. I don't want to just start replacing parts but I am at a loss, any help is greatly appreciated.

 

[Tim_MN]

Logical suspects:
- bad ground ( including any of the internal or external bulbs )
- short circuit to ground
- faulty ignition coil
- failure of an auxiliary circuit board like key-less entry

Failure of the drivers door and tailgate wire harness leading to short circuits is very common. 12 volts positive shorted to speaker wires can cause all sorts of interesting issues.

 

[JMA_2001XJ]

Logical suspects:
- bad ground ( including any of the internal or external bulbs )
- short circuit to ground
- faulty ignition coil
- failure of an auxiliary circuit board like key-less entry

Failure of the drivers door and tailgate wire harness leading to short circuits is very common. 12 volts positive shorted to speaker wires can cause all sorts of interesting issues.

ok so I separated the yellow and red power wires from the radio harness to the oem harness as well as the ground wire. Twisted the yellow and red together from the radio harness and connected them to a separate 12v battery and took the ground wire from the radio harness and grounded the wire to the negative of the separate battery and everthing is fine. So would you say it's the coil??

Also previously before this test I had tried separating the radio ground from the factory harness and then running the ground wire from the radio harness to the xj's battery and it still continued to make the crackling.

 

[JMA_2001XJ]

so after more investigating it turned out to be a the speaker in the door came loose and was grounding out against the door itself. stupid.