Sound system static noise when revving engine out

Hey guys I noticed recently that I get this intermittent crackling or static happening whenever I'm pushing the car past 7000rpm on the road and the sound system is on.

Im 100% sure my amp is dry and my tail lights are not leaking as I just changed the seals on them.

I suspect ground strap. How do I even go about fixing something like this? There are more than one ground strap correct? My exhaust one non existent but I hear those aren't important.

I'm thinking maybe the main one near the collector under drivers side? Or maybe whatever other one there is?

I was also suffering from a no crank no start problem, so changed my battery since it was overdue anyways. I THINK this fixed that problem but not sure.

Anyways the crackling is intermittent, it's just kinda annoying when im listening to music and driving hard. At first I thought it was trim vibrating or creaking but it comes from my back speakers and front left speaker as far as I can tell.

The ground strap nearest the driver’s side header is easily accessible once the belly pan is removed. I replaced mine after a persistent slow start-up despite a new battery, and it was indeed the solution.

There's two additional ground straps on the rear exhaust. I would say these are important as the redundancy is crucial for any compromised connection.

RocketyMan wrote

There's two additional ground straps on the rear exhaust. I would say these are important as the redundancy is crucial for any compromised connection.

Thanks i will try to replace all of em

Taking them all off and cleaning the ring terminals with a wire brush might help substantially as well.

RocketyMan wrote

Taking them all off and cleaning the ring terminals with a wire brush might help substantially as well.

Yea i suspect its just corrosion, because until yesterday I drove my car all weekend revving it out, taking corners fast and had 0 problems while listening to music, until yesterday it did it again when i was turning left on an on-ramp but it wasn't as bad as the week before.

It might also be worth checking the alternator terminals too. Any compromised connection could translate into buzzing noises through the radio.

Good info. Static is annoying. Thought I was the only one. LoL

GcD wrote

Good info. Static is annoying. Thought I was the only one. LoL

Glad to hear its not just me. Surprisingly mine has gone away, but taking it to mechanic on Monday to do my valve covers + vanos covers + starter + grounding strap since theyre there working on it.

Will report back to let you know if it solves my problems!

Also, replacing battery did not fix my no-start problem, but the no-start issue has gone away for now. Still suspect its my starter because last time it happened i just let the car roll back in 2nd and let clutch out to move the flywheel around and voila it started again.

The amp can be damaged by heat also, not just water. Try disconnecting the amp and see if the problem goes away.

Redd wrote

The amp can be damaged by heat also, not just water. Try disconnecting the amp and see if the problem goes away.

Umm ya...how exactly would this help when the amplifier is the only thing powering the speakers and there's only one connector?
(Barring the MOST connector)

RocketyMan wrote

Umm ya...how exactly would this help when the amplifier is the only thing powering the speakers and there's only one connector?
(Barring the MOST connector)

Lol exactly?? Dont know what hes talking about.

Anyways, it kinda fixed it for the most part, it doesnt happen as often, but also my starter was totally about to fail, so glad i replaced it.

Not sure what to do now. Maybe i need to ground the exhaust too, not really sure.

interlagosbluee92 wrote

Lol exactly?? Dont know what hes talking about.

Anyways, it kinda fixed it for the most part, it doesnt happen as often, but also my starter was totally about to fail, so glad i replaced it.

Not sure what to do now. Maybe i need to ground the exhaust too, not really sure.

Yeah look at the rear muffler section of your exhaust. There's supposed to be two ground straps. Confirm they're there and not crusty.

Look at #10.
https://www.realoem.com/bmw/enUS/showparts?id=WD93-USA-11-2009-E92-BMW-M3&diagId=18_0747

RocketyMan wrote

Yeah look at the rear muffler section of your exhaust. There's supposed to be two ground straps. Confirm they're there and not crusty.

Look at #10.
https://www.realoem.com/bmw/enUS/showparts?id=WD93-USA-11-2009-E92-BMW-M3&diagId=18_0747

I haven't used those ground straps in like 7 years.

Not: ideally the ground band you want to replace is the interference suppression band that is inside the engine bay if static is the concern, but replacing all the grounds is good practice since they are cheap and easy to do.

I believe its the cable from the hood to the chassis, driver side.

omgzirra_exe wrote

I haven't used those ground straps in like 7 years.

Not: ideally the ground band you want to replace is the interference suppression band that is inside the engine bay if static is the concern, but replacing all the grounds is good practice since they are cheap and easy to do.

I believe its the cable from the hood to the chassis, driver side.

Ya true. There's also a ground strap on the hood. Also on some boot lids.

How are you so sure amp is dry?

I only ask because I was pretty sure also when I had my amp dead. I inspected frequently without disassembling many parts, but was only deducting, not really seeing. When it died, I was obligated to disassemble, and there was the water.

RocketyMan wrote

Ya true. There's also a ground strap on the hood. Also on some boot lids.

Noted thansk guys I had no idea there were more grounds.

jvictormp wrote

How are you so sure amp is dry?

I only ask because I was pretty sure also when I had my amp dead. I inspected frequently without disassembling many parts, but was only deducting, not really seeing. When it died, I was obligated to disassemble, and there was the water.

Im not saying it isn't, but I'll have a look. I just know because I changed both tail light seals.

Anyways, i have a feeling its the engine bay strap you guys are talking about. Seemed to come back yesterday when it was raining, but again it's not as bad as it used to be.

It might also be worth cycling the connectors on the amp to re-establish a good connection. Even if the area is "dry" next to the amp, it could've still got moisture at some point causing a little bit of corrosion to things like the connector. Temperature change and weather may seem to reinforce a compromised connection.

I've used this spray called Deoxit to help clean and clear any debris or oxidation film with good success. Enthusiast use it for this very sort of thing on guitar amplifiers and such. This may help for the connector and contact pins.

https://caig.com/product/deoxit-d5s-6-lmh/

RocketyMan wrote

It might also be worth cycling the connectors on the amp to re-establish a good connection. Even if the area is "dry" next to the amp, it could've still got moisture at some point causing a little bit of corrosion to things like the connector. Temperature change and weather may seem to reinforce a compromised connection.

I've used this spray called Deoxit to help clean and clear any debris or oxidation film with good success. Enthusiast use it for this very sort of thing on guitar amplifiers and such. This may help for the connector and contact pins.

https://caig.com/product/deoxit-d5s-6-lmh/

Thanks I ended up trying this but it didn't do much. I don't have the problem really anymore unless I have my little bluetooth to aux thing plugged in to charge it, and even then it's not as bad as it used to be. I still think it's probably a grounding problem with the exhaust.

My hood grounding strap was in perfect condition.