How to troubleshoot ignition noise?

[AudioGeek]

I have checked everything, cleaned all the grounds twice, put brand new star washers everywhere, and I still have noise from my head unit, but no noise when I play an ipod directly hooked up to my amp, with the same RCA cables that run to the head unit. Also tried grounding the RCA cables, even though it's a brand new Alpine deck. Didn't work. I never unplugged or plugged the RCA cables while anything was on anyway. If the battery was ever on, I at least had the head unit unplugged.

I'm pretty sure it's ignition noise, it's a vibration sound from about 150Hz-800Hz that stays at a constant level, so I can mask it by turning up the volume. I also ground my head unit to some metal under my steering wheel, where there is a lot of vibration. I do have a tiny vacuum leak due to my smog pump that is going out, but I minimized it by clamping all the hoses where the air was leaking.

Anyway, how do you troubleshoot ignition noise? My wires, plugs, cap & rotor, and coil pack are all MSD, brand new about 9 months ago, about 9K miles ago. Also got a brand new battery at that time. I have a 200+k mile American car, so my friend said I probably would be better off replacing the whole distributor, but I would think I shouldn't have any ignition noise with so much brand new stuff.

I think it might just be the head unit ground. The metal under the steering wheel area is probably not the greatest place. I can't really find anywhere else to add a ground though. I rather not drill a hole under the carpet. I don't have a jack to check what's under the car, and my drill is not the greatest, so it already had a hard time drilling through the metal near the steering wheel.

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[dumple 5,000+ posts]

Headunit brand?

 

[kramer_212 10+ year member]

i would just get a new head unit, i have had multiple alpine head units that have had noise problems.

 

[AudioGeek]

****. That's funny because I got rid of my Pioneer that was working fine.. and got this Alpine with the noise. The Pioneer actually wasn't working fine though, it was only outputting low frequencies out of the preout. It had no low pass filter on it, so I think I had just blown the outputs or something, because there was one hot day where the head unit shut down after playing a lot of loud music. (still had my mids and tweeters powered off the deck) The Pioneer did have no noise though, that was nice. And it was running to a factory ground. I had to make a new ground for this head unit, and it still won't work.

I really rather not swap head units again though, because then I'd have to get a new wiring harness and cut/splice/run my speaker wires all over again. (I ran my speaker wires from the harness just so it would be easy to switch it back if I ever sold the car). The wiring harness has been cut about 4 times, just since I had the car, for various reasons, so there's no slack left on it.

 

[trumpet 5,000+ posts]

Wiring harnesses are cheap, and if you ran your speaker wires to the harness I don't see why you'd have to run the wires all over again. Try the head unit out of the vehicle, powered off the battery only. You can hook up one speaker to listen for the noise.