Flutter/Rattle Sound With Moderate Throttle

[Ajolives]

Originally Posted by Zeesh89

Thanks Redd

My mechanic had a knock around there a few times but couldn't see anything loose - he also had a knock around on the cat but didn't notice or hear anything loose there either.

Hi Terence, did you manage to make any progress with the dealer?

I had a very similar noise and thought it was a bad catalytic converter - ended up being bad exhaust gaskets (the donuts) and worn hardware.

When I inspected the noise it sounded like it was coming from inside the cat, and everything was tight, no rattles when I gave everything a shake. Thought it was a bad cat (125k miles) so I bought a aftermarket x-pipe and went to install.

There was basically nothing left of the drivers side gasket and the space between the pipes where the gasket should have filled was causing vibrations that would culminate near the cat. Or at least that was my conclusion. Haven't had the sound since and keep some backup parts in case it happens again.

Not saying it's your problem for sure, but if I were a betting man….

[Ximian]

Originally Posted by pp276

Zee, your video is the exact sound I've have for last 5 years of ownership! It's been hard to make a recording as seems to come and go but always at low speeds under light throttle, for example, up parking ramps or in stop-start traffic. Really embarrassing but does not seem to affect how the car drives.

I've had it checked by 3-4 mechanics, including a thorough look at my stock exhaust, with no joy.

I'd be very interested in any progress you guys make!!

I've had this sound too for a while.

I've also had the codes 2739 and 27C5 that I attributed to the sensor/hose kit and the secondary air pump. I heard the next step for those codes is the secondary air valves and that makes sense with the noise I've been hearing at moderate throttle.

[Zeesh89]

Hi All

Thanks for your feedback.
I took it to another bmw specialist who told me it COULD be engine pinging (though that was a guess) ....from what I understood this comes down to carbon building up in the cylinders (or something like that) - i am not too technical with these things.

They also said they couldn't find any thing by doing an inspection.
Any thoughts from anyone else would he appreciated.

Many thanks and stay safe.

[DOCTOR.Y]

Do we have any finding? I have this noise also.

[SilverSlug]

I also have a similar noise, as well as the fluttering noise (especially at start up when the parts are cool and haven't expanded yet).

It finally got to a point where the Check Engine Light turned on and warning disclaimer for "Reduced Power" (limp mode).

[SilverSlug]

I assumed the leak was coming from the junction of the headers to the mid pipe as so many others have that same leak…

I had taken a rubber hose, and used it as a stethoscope to try to isolate the noise by sticking it around by that junction, and realized it definitely wasn't that.

I could clearly hear it coming from underneath the heat shield on the driver's side, and can only assume it's from the headers at the manifold.

Although perhaps it is the emission valve, and it just finally gave out all the way (or both).

I'll update what I find.

[shyterence]

Hi, I am still driving with the noise with me...can you guys solve the issue?

My mechanic told me the noise is related to carbon build up, so I leave it there...

[Zeesh89]

Reviving this Old thread in case anyone has experienced this issue as of late. The rattle seems to be quite obvious and is making the drive of the vehicle much less enjoyable

Thanks
Zeesh89

[De_Cruelz]

I've had these annoying rattles for a good few years now and seems to get progressively worse. Sounds identical to the videos Zeesh89 and renaissance posted in the carpark. Not just annoying, it ruins the driving experience and sound of the V8 that we all love.

Hopefully we can narrow down the issue here and resolve this once and for all!

As most folks have mentioned and similarly for me, it happens when:

1) Car is fully warmed up. As it's warming up closer to the operating temp, I start to hear it but just not as loud. Perhaps this may be a clue to something?

2) Usually low RPMs, from 1500-3500rpm.

3) On an incline, up a ramp. This one is particularly loud. On longer uphills, it rattles the whole way unless I get out of the rev range.

4) In traffic, accelerating from a full stop or low speed, like the carpark video.

It doesn't however happen from a cold start. Gentle driving for the first 1/4 to operating temp - no rattles. As above, when approaching maybe 1/2 to 3/4 to operating temp, the rattling starts getting louder and louder.

What I've done to troubleshoot the issue:

1) Initially, most folks seem to think this is fuel related causing pinging/detonation. There's a long thread about it here. Looking at the last update, it appears the OP resolved the issue with a tune, which adjusted the VANOS. What that entails, I do not know or if the VANOS can be adjusted without a tune.

2) I've tried all ron98 fuels we have here in Sydney. Have also tried a variety of fuel injection system cleaners and octane boosters. Octane boosters seems to help reduce the rattling slightly, but I think this is more due to the engine running a bit smoother through the lower revs, less lugging and therefore less likely to trigger the rattling sound. It kind of feels like a certain low RPM range and exhaust sound frequency that triggers the rattling the most. Engine feels more responsive with the boosters but rattling is not completely gone.

3) I've had plugs, coils, injectors, O2 sensors replaced and Vanos sensors cleaned and yet the rattle remained. I don't think it would be related but also have had rod bearings and throttle actuators replaced as preventative maintenance.

4) Stock 240E and 241 software and also have a BPM stage 2 tune. No change with the rattling. This is partly why I'm not fully convinced it is tune related as per point 1 above. Perhaps OP there is having a slightly different issue.

5) I've had 3 different catback exhaust setups and it rattled on all of them. Always used new gaskets when I swapped the exhausts out. Exhaust manifold or heat shield around the headers is a good guess and one I have not explored. Come to think of it now, as the car warms up and with expansion from heat, something may have gone loose and is causing the rattling noise.

Other troubleshooting to rule out the issue:

1) I recall our forum friend Redd suggested using an OBD2 dongle and Android app called Torque to log ignition timing. I don't have an Android device but if someone else here does, definitely worth looking into. Redd if you can help confirm, is it this paid version here?

2) Check the exhaust manifold heat shield and gasket. Perhaps with heat, wear and tear over time something may have gone loose or broken?

3) Most expensive option which is the emission valve mentioned in this thread, although seems unlikely as the noise it made is different? Also so far my engine is generally running great and I don't have any error codes either.

Very keen to hear everyone's thoughts on this. Hopefully with the above, we can get closer to getting rid of this super annoying rattle once and for all and we can enjoy the V8 in all its glory!