Thought I might share my experience with solving this problem. Let me lay down some information first:

1. Here is the sound I'm referring to - this "Marbles in a Can" sound was associated with noise above 7k RPM typically under WOT. It was not associated with power loss (if so, it was minimal).

http://www.youtube.com/watch?v=bm3NcgTnmRk

You can hear it best on his first "pull"


2. I don't know if anyone has outright reported that cleaning the MAF has helped but here are my results anyway!

3. I have a 2006 GT 6 Spd with 38K miles. I do have a K&N Air Filter which I know was not recommended by member teknics due to the fact that there is some oil in the K&N filters versus dry filters.

I used some Precision Electronics Cleaner from radio shack and sprayed it on the metal on the MAF (technical term). I found when I pulled out the MAF that there was black film on the leading edge of the metal thing. I sprayed the cleaner on the metal thing and cleaned it all off. Put everything back in and took the car for a spin.

Problem solved! No sound under WOT at high RPMS in any gear, just the smooth sound of the rotary whirring up and sucking in air

P.S. the traction light comes on your dash if you disconnect the negative terminal - turn the steering wheel all the way to the right then all the way to the left and the next time you start your car up the light will go away.

 

Thanks for your post...

There are also a few other factors that can cause a "Marbles in a Can " sound...

You can have worn out or bad spark plus, coils, or Spark Plug Leads which break down under high load or RPM.

Then there is a more "Grinding or Crackling sound at High RPM, this can be detonation, as the Fresh AIR through the Throttle Body gets too hot, particularly in Summer Temps.
As we know the Throttle Body is Heated by the cars Cooling System, one to prevent icing during Winter and two because of Emissions, many block or bypass this event so your TB does not get so hot.

The other issue can be a High Carbon build up on your Rotors and or Spark Plugs, the Rotors can be "Cleaned" by the Seafoam Procedure or "Steam Cleaning" methods posted in our Forum...do a Search.

As we know the best way to prevent or at the very least tame Carbon Build up is to Red-line your Rotary when the engine is at NORMAL Operating Temperature at least once or twice a day or when you use your car.

Pre-Mixing also Lubricates your Apex Seals and Rotor Springs which can also help to prevent high Carbon deposit Build up on the rotor face...DO NOT USE A MARINE/BOAT TCW 2 Stroke OIL or Castor Base Oils..

 

Ok, i've got a similar problem, but different. Mine makes kind of the same sound, but only in gear, and i doesnt do it in first...(mt). Comes from up by the engine, at around 3-4k rpms. Anyone had that prob yet?

 

remember MIC can also be detonation if using low octane fuel(below 91 oct.)

dmashuda...we need some more info..what yr 8? under WOT at 3-4k or anytime?

 

I was having this problem at 5.5-6.5 krpms, i put in a can of BG44k and it went away for about 3 tanks. It is back but only in the higher ranges (around 8k), maybe this is due to the 100+ degree weather we are having.

 

^are you using at least 91 octane?

 

I just put a can of BG44K in my tank more for preventive maintenance.
My new tech guy says one can at every oil change.


If you are getting the marble sounds again after 3 tanks of gas you may need another can because there could be more carbon in there still but check with a mechanic first because I don't think you are supposed to use it very often.

 

^seafoam is the same stuff and cheaper i believe...8 or 9 bucks for a can

 

Yes sorry guys i wasnt very specific in the first post. First of all, i always run 91 octane...always...And the rattle only occures at about 3/4 throttle...it almost sounds like one of the fans brushes the radiator for a second. Thats a perfect example of what it sounds like. Im not sure if it did it before i put my borla cat back on or not. Might it have rattled some carbon loose in the cat? Its an 04 with only 25k on it tho. Shouldnt hardly have carbon in it yet lol!! And the borla system isnt hitting the diff, i fixed that on the first 8 i had it on, So that also means that it doesnt rattle cuz my other car never did. So any other ideas? Otherwise im gonna have to take it in ;(

 

Ok, so i went for a cruze today and of course it did the little rattle thing at first. I pinned it down to 3500-3750 rpm. As i drove around however...feelin kinda racey...hit a few 110mph marks...it stopped doing it under normal driving conditions. So could it be the water pump cavitation issue?? Doesnt really sound too loud yet or quite as harsh...im not sure?

 

i am having this same problem.

09 rx8 r3
Renesis series 2
6spd manual
91 octane always
Great compression
Seafoamed every 3-4 fuel ups
Redline far more than required

Symptom:
MiC above 7.3k RPM at WoT. Severity of sound is random and have found no connection to cause of the different intensities of sound. No notable power loss or warning lights during MiC sound in any gear. Duration within the problem range had no effect on engine behavior tested all gears WoT to redline (except 6th due to speed limiter at 149mph)

I will try cleaning my MAF to try verifying if this is a common/repetitive issue or if the problems lay deeper.

PS apologies for necroing the thread but this one matched perfectly to my issue and see no reason in creating new thread for same topic

 

Well often people are different in their perception of what the actual noise and cause of it is as well as the perceived correction. It could be pre-ignition/detonation which then you have to assess any number of other parameters such as pcm fault codes, actual sensor data and so on to have any clear idea of what might be going on. For some people the noise was cavitation in the heater core/coolant system and installing a factory restrictor into the coolant line solved it (seemed to be missing). Otherwise the only way to respond based on the information provided is to guess. Which typically you can expect a bunch of ‘guessing’ replies at some point.

 

i cleaned my MAF and the sound is much quieter now. It occurs above 8.5k now instead of 7.3k. When I get a chance I will look into cavitation in my coolant lines as I am getting a coolant level error in 6th at WoT. And would assume the cavitation is causing sensor malfunction

Edit: after spending much time searching around for this issue else where I stumbled across this:

MAIC, or "Marbles in a Can"
... is a fortunately not common issue where you may hear a rattling sound from what sounds like the glovebox area, sometimes accompanied by inconsistent power loss. This is usually Secondary Shutter Valve (SSV) failure, which is typically caused by the valve getting over carboned, from oil burping or oil excessive oil vapors in the intake. Dealers will charge $2,000 or so to replace/clean, but you can DIY it for pretty much free.

so although it is not a "common" problem it does occur frequent enough to be noted and posted in a common rx8 issues log.
good news is it really cheap to fix ourselves but going to cost you some time.



Also found this in reference to the coolant cavitation/coolant level light:

Faulty Coolant Level Sensor:
The coolant level sensor in the coolant bottle is prone to failure, allowing the float to sink to the bottom of the coolant bottle regardless of how much coolant is in the bottle. If your coolant level light comes on below 7,500 RPM, and you have sufficient coolant in the bottle, then the coolant float is water logged. Fixing this requires replacing the coolant bottle, since the sensor and float are integrated into the bottle. Mazmart.com has a replacement bottle for relatively cheap. If the light comes on above 7,500rpm only, then you may be experiencing a cooling system failure that is creating a restriction and/or water pump cavitation instead.

 

Actually i think i've found the solution to cat failures on the RX-8. I recently experienced the glowing 02 sensor, thinking it might be clogged catalytic converter, plugs, coils etc, also had the "marbles in a can sound". It turns out it was the type of gasoline i was using. Here in Europe its normal to fill with 95 octane, which is also what is recommended for the RX-8. After i switchted to 98 octane from Shell, the cat stopped glowing!! I tried to abuse the care many times, but cat still not glowing. Try some proper fuel, i bet it fixes the issue! Is the RX-8 ment to be fuelled with 98 octane? I think so.

Can anyone else confirm this?

 

Cats eventually die in any 8 I think.High Temps shred them. Bad gas certainly adds to that. Not regarding miac per se, but here in Greece, until some time 98 shell was decent. The new year batch though is crap. Shell here is just a brand, corporate shell has left the building. So it's the same gunk in those reservoirs and they add shell approved additives to raise octanes. It's not a true 98 pump gas anymore. In fact I don't think it's even 98 ron.
Premixing helps a lot here.
So, I hope you keep finding good gas because I read about pump gas issues around the world. Watch it and update if anything changes.

 

If you were getting detonation on 95 that was fixed by using 98 .... I'd suggest you have other issues . For example , a heavily carboned up engine.