Playing music through iPod 4 USB makes occasional static popping sounds

So I connect my iPod 4 using USB to my car. But as of the last few weeks, when I play songs on it, I hear an occasional static popping sound as the music is playing. The static is just a light click/pop, randomly every few seconds or so, and it's somewhat unnerving because I don't recall having this issue when I started using my iPod in my car.

I tried switching to another connector, and the same thing happened.

But when I play music using the auxilary connection, that is, through the 3.5 mm audio jack on my iPod, that music comes in with no static-like pops.

I checked both connector cables, and they look fine to me. I checked the USB port at the the car. I also tried wiggling the cable while music was playing, but wiggling didn't create any more or fewer popping sounds.
What's going on?

 

It's plugged into an iPod dock connector. I set it in place and leave it there for the ride. I tried wiggling the connector cables but that doesn't seem to do anything.

 

Alright here's a video so you can see my connection and actually hear the pop sounds without other music playing on top of it.
Video - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting

 

Interesting. I'll see what I have laying around. I'm not knowledgeable enough to get into the mechanics, so what kind of grounding screw could I use? Could I just run a wire around the outside body of the car and hold it there? (Edit: Actually wouldn't a tire cap work?)

Not yet. If the issue is my iPod... then there's really nothing a dealership needs to do. I want to rule out my iPod first, since I have no issues using the 3.5mm analog on it.

 

Well I have somewhat inconclusive results. Grounding the iPod shell seemed to work (maybe one pop over the span of a few minutes)...
...but then when I returned the iPod to its original "it makes popping sounds" setup... I again heard only maybe one, or two, pops per minute.

 

I removed the grounding wire. The iPod stayed in its dock. There is a soft plastic shell around the iPod.

So, I kept the ground wire on the iPod shell for a longer time (5 minutes) and I had the volume up pretty high. No popping.
But again after I removed the grounding wire, the popping didn't seem to come back either.

 

So what do you guys think? Is my iPod connector damaged, and need to be repaired?

 

Alright well this is bewildering. I did those grounding tests a few weeks back...and then I didn't bother to use my iPod since then. I went back to using my iPod like normal again today, and I haven't heard the popping all day. I guess the problem remedied itself.