I don't think there's anything wrong, it's just a sound that's always annoyed and puzzled me, and wondered if there was an explanation?

It's a faint tinkling sound from the engine, only heard under light throttle when putting a strain on the engine, like when accelerating from low rpm's in 4th+ gear. I don't hear it at high rpms, and it dissappears when off the throttle at any rpm or gear.

Kinda like... pouring small screws into a jar, or dumping a bag of M&M's into a glass, or spilling loose change into a cup, or... you get the idea. If you've heard it, you know what I mean.

I don't think it's the infamous "marbles in a can," as it's very faint. Too faint to record even.

I used to think it was engine knock, since it only happens when straining the engine (low rpms, higher gear, push gas pedal). But it's always done it, and I use premium only, and have a new engine with new plugs/coils/wires and SSV.

So I'm thinking it's a "natural" sound of some gadget on the engine, just curious what it is?

 

sounds like classic MIAC to me .......

 

Well maybe, but I always thought MIAC was a rather loud, scary sound when your catalytic was failing?

This sound isn't scary loud, I doubt a stranger would even notice it actually. It's faint and distant, only noticed if the radio is off and things are fairly quiet in the cabin.

 

I think I can relate to what you're speaking of. Is it a very small, light 'ringing' noise??

If so, I've been curious about the same noise... But I never bothered to bring it up since I always thought it was normal, as well.

Curious to some answers though.

 

Just make sure you're premixing at 1/2 oz per gallon.

If you haven't premixed, try it and come back with info.

I'm a fan of hitting the seal lube from two directions.

My RX3 had sort of a whirring sound while easing around, lasted 75k before water seal leak, and I should've premixed, but didn't think about it back then.

 

That's exactly it. Nothing alarming, just a little annoying once you notice it. My only concern was that it was from engine "pinging," just because it only happens when straining the engine at lower rpms in higher gears.

Reading around, it seems the MIAC sound is mostly at high rpms, is rather loud, and sounds a bit like sand or popping at times. This isn't like that at all, it's a faint ringing, tinkling noise.

I've just never ridden in another 8 before (odd, isn't that, in all these years lol), so I have no idea if it's normal for an '04.

 

^ I used to have a '04 RX-8 (auto tranny) several years ago, and as far as I can remember, I think I recall the same noise... I'm thinking it's natural to all RX-8's, but don't quote me on that since I've been wrong before, lol.

I'll stay tuned to hear some more opinions & answers from our members here.

 

Then don't do it

 

I'm pretty sure I've noticed this same thing, the sound is barely perceptable so I don't think it's MIAC. I also have an 04 AT, so it's possible that it could be a 4 port or AT specific issue.

 

I think I have the same sound. Only in first taking out and possibly slightly in second on occation. I didn't think it was actually engine. I thought it might be a heat shield on the exhaust vibrating slightly. Oh and mine is an 04 manual.

 

i get this as well when in 6th gear, thing is although the rpm is low im pretty sure at the particular speed the car is traveling and the forward momentum its in, im not lugging the engine.

 

thats right, throw out subjective solutions without knowing the problem, if there even is one.

 

MariesRX8, I think a video or audio recording would help tremendously.

What you're describing doesn't sound like MIAC.

I don't think I've experienced what you're describing because as Tamas pointed out, I try to be diligent about keeping engine loading low below 3500 RPM.

It might help to get an assistant with a mechanic's stethoscope to at least attempt to probe the general location of ground zero. Is it in the engine bay, transmission tunnel?

 

My hunch is that it's transmission noise (the tinkling), which I hear, and is normal.
To check, see if the sound stops when you depress the clutch.

 

Yes, I've been experimenting more, and it does go away with the clutch in.

I hear it whenever moving and in gear, even when just coasting. It's most obvious when getting on the gas at low rpms, but is still there at higher rpms too... it's just harder to hear over the engine then. And it's fainter when just coasting in gear, but still there. But push in the clutch while moving... and it's gone.

Never hear it in neutral, whether clutch in or out, revving it or at idle. Only when in gear and moving.

So I guess you're right about transmission noise

 

If the sound still bothers you, it might be worth a try to change gear oil to Redline synthetic MT oil (I forgot the number - should be somewhere in this forum). It could smooth the sound a bit. I've been meaning to try this, but haven't gotten around to it.

 

It is detonation. There was a thread where I explained this like two weeks ago.

 

Detonation even when coasting? It seems unlikely.

 

Are watching your calculated load? If not you really don't know whether you are "coasting" or not.

 

MariesRX8, if you don't have a scanner handy for calculated load readings, try coasting somewhere downhill or decelerate (engine brake) in gear and see if the sound is still there.

Engine braking causes "negative" loading and IIRC, our cars shut off fuel and ignition when this happens (to save fuel I think). There's no chance detonation can happen if this is true. If you still hear the sound, transmission noise is likely culprit.

 

I have heard this noise since my car was new (10/2003) and figured the stationary gears being straight-cut might have something to do with it. Maybe transmission lash, too.

 

Ah, good info. I didn't know one of the gearset was straight cut. That's what it sounds like.

 

Yes, still there when off the gas coasting downhill, low rpms or high. Only much less noticeable when coasting. Much more obvious as soon as I touch the gas pedal. But it's always there, to some degree, when moving in gear.

It's sporadic though, it was barely noticeable for my morning commute, but then very obvious for my drive home... until I stopped for gas. When I started it again at the station and drove home, I could barely hear it. Like turning the car off and on "reset" it somehow.

I'd think a tranmission noise would be more consistent? Plus the noise itself isn't a constant whine or whirring, it's a random tinkling/rattling noise, kinda like I'm dragging a very small metal chain along the road. And the pitch doesn't vary at all with gear or engine speed, it just gets louder when you touch the gas pedal.

I guess I'll end up at the dealer with it, I was just hoping to narrow it down a little to avoid a huge diagnosis fee. The more I read, the more it could be soooo many things, from perfectly normal, to intake valves (my SSV is new though), exhaust leak, heater core something, heat shield rattle...

Or maybe I'll just live with it, as the car starts and accelerates perfect now with the replacement engine. I think that's why this "little" thing stands out so much lol, it's not a big deal, but it's the ONLY thing "wrong" with the car.

 

I was gong to suggest Fuel/gas, octane too low.

Or, I am thinking Spark Plugs, their age (carbon-ed up), IF you are driving around and not going higher than 3500-4000 RPM, definitely Spark Plugs and I feel sorry for your engine, Oh it is an Auto, even more so, sorry.

 

Mine has done this from new, after the engine has warmed up, under light throttle up to about 3500-4000 rpm. It cannot be heard when the engine is cool. Occurring since new and under light throttle pretty much rules out carbon or octane related pre-ignition. I've always thought it sounded like it might be some kind of catalytic converter rattle or resonance. Strangely, it only does it when the torque converter is not in lock-up mode, and the noise goes away when the converter locks up in 5th and 6th gears. I'm wondering if the ignition timing curve changes for lock-up mode in these gears, and alters the exhaust resonance through the system, eliminating the noise.