I finally got annoyed enough at my CD changer to pull the thing out of my car. I installed a Pioneer AVIC-Z140BH Navigation system. Everything seems to work great...except the radio. Anytime I listen to FM (I've never tried AM but assume the same) I get a popping noise that is in time with the engine speed. This does NOT occur when listening to XM, CD's, MP3's, or Bluetooth audio.

I've tried installing an in-line power filter and it had absolutely no effect. I also tried installing a ground loop isolator on the antenna input and the problem increased 10 fold. This leads me to believe I may have grounding issues. When I installed the radio I used the harness ground as well as a stud on the bottom of the dash frame that showed good continuity to ground so I'm not sure why I would have ground issues but I'm at a loss as to what else it could be.

I have about 15 feet of 8 gauge stranded copper wire and was thinking about running a new ground to the engine and to the dash. Does anyone have any thoughts on the best way to go about this? Anyone else have similar problems they were able to fix and how did you go about it?

 

Cheap wiring leads to interference. Really need good shielding or you will hear interference. How long is your ground? Should not exceed 2 feet as a rule of thumb. Go back into your wiring and replace if you used cheap stuff. Should fix it. Cheap RCA cables are the leading cause of interference btw

 

The ground wire I'm using now is only about a foot long and is the harness cable for the stereo. I had thought about noise filters on the RCA connections but since the noise is only there for FM and not for anything else I kind of ruled out a problem there...unless you think otherwise?

 

What RCA cables are you using and is it running next to the power wire?

 

I'm not using any RCA cables. The only RCA connections I have are directly from the stereo to a Metra 70-7551 Amplifier Integration Harness. I'm still using the factory BOSE amps and speakers.

 

You mentioned RCA connections so I assumed you had some. Metra kits use cheap stuff. I would take it apart and insert higher grade wiring. Obviously somewhere in your wiring interference is being let in due most likely to no shielding or cheap shielding. Find it and fix it. Dont know how you wired it so I can not tell you without asking a million questions and I dont want to do that

 

Fair enough. I'll see what I can find. The RCA wires on the harness are only 6-8 inches long. I don't see how they could be picking up that much interference. I would also think it would occur in all my audio and not just FM. I may have a set of high end RCA's I can cut and use to rebuild the harness though and see if it does anything.

 

Well, usually interference comes in when wires are too close together and with cheap RCA's next to that many wires it can happen. Its hard to say, but likely too many wires bundled next to each other is causing it. I would scrap the harness as a whole and just solder the wires to together separately so there is some air in between them. If you pop it out and take a picture then maybe I can see where it is coming from.

 

I didn't really want to cut the factory connectors off in case I ever wanted to sell the car and put the factory radio back in. I'll try to get some pictures of the connections this weekend and get them posted up. I'll still go ahead with trying to improve the ground. It might not help but it can't hurt.

 

Ground to chassis behind radio

 

I was thinking of running a new, separate ground cable from the battery to the engine block and from the engine block to a terminal block behind the dash using 8 gauge cable. I could then connect all of my grounds (Nav, XM, steering wheel control adapter, power filter, traffic tuner, and so on) to that terminal block. I could also run an 8 gauge ground from the terminal block to the Nav chassis. I've got 15-20 ft of 8 gauge power cable from an old amp installation I pulled out of my old car, I'd just have to buy some ring terminals for it.

 

That is a bad idea. A chassis ground is always the best ground. Do not ground more than 2 things in one place either.

 

Make sure your spark plugs have resistors in them. Plugs without resistors cause large amounts of EMI. I don't know if they even make plugs without resistors for cars though

 

It has OEM spark plugs and there was no engine noise before swapping the head unit.

 

How would you recommend I go about improving my ground then? As I said before I'm already using both the original harness ground and a bolt on the frame that showed good continuity. The double DIN adapter I used came with plastic brackets that replaced the original steel ones. Could this be part of the problem? I tried using the metal brackets but I couldn't get anything to line up properly with them.

 

Well it looks like I finally have it all cleared up. I spent three hours yesterday going through all of the wiring and checking my connections. There were two t-splices on the power side, I replaced those with crimp caps. I also bypassed the ground in the factory harness altogether and ran three new 12 gauge ground cables to three separate points on the body, including one to the factory grounding point below the left A pillar (M9). Now all the radio stations come in crystal clear, and I'm getting stations I didn't even get with the factory radio. I also found a loose connector on the Bose subwoofer that was causing it to cutout. Thanks for all of your help.