KKMmaniac

(posted by SlowLude) "I'm not too worried about it cuz I accelerate slowly through the RPMs and then do it again faster, I don't hear it. Strange."

Yep, mine exhibits the same behavior. If I romp on it, (and hear the rattle)
then later in the drive romp on it again, the rattle diminishes or disappears.

Maybe the PCM retards the timing from the onset of pinging until the drivers foot gets lazy again for a period of time. However, I don't care for the noise at all, and probably either does the engine!

cbucalo

Glad someone finally mentioned CEL. I've been hunting around looking for some info on this. I drove up to Norwich NY from Allentown yesterday and decided to try some hard accelerationons on the tpike. I got it up to about 110mph when I heard/felt "clatter" under the hood. Almost sounded like it traveled back and fourth under the hood too. The CEL flashed a few times, then it all went away. I couldn't get it to do it again. I was thinking of taking it into the dealership to see if it recorded something and if it could be diagnosed. It had about 1400 miles on the odometer when it happened. I'd been driving for a couple of hours at 80-90 steady. Think this a problem?

cbucalo

I feel the same. Did the search last night when I got home and, well, rattle doesn't really describe it. Still think its more like a "clatter". I didn't feel any change in power, felt/heard the noise: most unique, and then really focussed on the flashing CEL. Always use 93. Probably will take it in to the dealer and have them check, while they are removing the massive door ding I got on Saturday. Kill, kill, kill the guy who dinged my door! Argh...feel bad inside like puppy died. Kill, kill, kill the guy!

Go48

Sounds like the infamous random misfire. The dealer can pull the code and confirm. If that's what it is, they will likely replace the plugs and send you on your way.

cbucalo

I think the dealer replaced them as part of the new car prep when I bought the car. Gonna check the paperwork. If they were changed, is this normal for new cars with 1400 miles on new plugs?

Go48

Probably not, but you need to find out what caused the CEL. May not be a misfire. Only way to find out is to have the dealer read the error code(s) with their equipment, have someone else with a CANbus-compatible OBDII scanner read them, or buy a scanner and read them yourself.

Raptor2k

^oh well. I hope my engine detonates before my warranty is up?

Just put in another tank of 93 from a different gas station, still get the marbles at 7500.

SlowLude

I guess we'll just call them 'marbles' from now on!
I've never got a CEL before and I've been redlining it every now and then.
It sounds like it's from the passenger side center. What's wierd is that I tested it out today and I had a passenger sitting in the car and it didn't make the noise! WTF?

Raptor2k

^sounds from the passenger side for mine too...no CEL, I redline frequently....

It really bothers me how there's just about no input or explanations from the 'experts' out there, I'm having to take advice from my dealership to just try different gas stations

PWRCLOSER

I had the same noise . I put 93 octane and it instantly went away.

Raptor2k

Sigh...

Raptor2k

bump

TheColonel

Could be totally unrelated, but when I had an Integra I had a similar problem w/ a rattle only at certain RPMs. Turned out the resonator pipe was coming loose and just happened to vibrate at those RPMs. Probably not the same thing, but I figured I'd give my .02 ...

Raptor2k

I wouldn't doubt that. It does sound like something is coming off loose, and thus, rattling.

I'm still on my second tank of 93 from a different gas station, still have the rattle. Waiting for the tank to run out so I can get another tank of gas from a random gas station, and see what happens.

Rick

^ You could try 87 octane. If there is no difference in the amount of rattle between 87 and 93 it is probably not knock. The knock in my 8's engine was MUCH louder using 87 than 92.

N8theGr8

both 8's I've had made this noise between 6k and 7k rpm. I always figured it had something to do with either the tertiary port or the secondary inlet duct (open at 6250 and 7250 rpm respectively if I remember correctly).

This is on a MT, not sure if the same on AT.

Raptor2k

^mines between 7k and 8k rpms, yes, MT

not a big deal, but i'd rather just hear the rotary

Rudboy

I am also experiencing this noise on my 2005 with 5200 miles. A rattling is the best way to describe it for me but marbles works well to. It only happens between 7000 and 9000 RPM's for me. It seems to be located near the floorpan/dash area on the passenger side.

I only use 93 Octane and I buy from many different locations so I'm not sure it's gasoline, maybe I should go try some Turbo Blue gas at 113 octane and see if it goes away.. I have an appointment at the dealer next Tuesday...not going to hold my breath till they get it "fixed".

Raptor2k

I'd appreciate it if you could update me tomorrow on what your dealer has to say.

Rudboy

They of course didn't fix the problem at all. I don't even think they tried. I do have another appointment for next Tuesday with the service manager who supposedly is going to work on the problem with a Tech until it's solved.

Will update.

Raptor2k

They told me to just try out different gas stations for two tanks, that didn't help me either, I'll be going back soon

N8theGr8

I still feel like it has something to do with the secondary inlet duct. It's consistent with every 8 I've driven plus the 2 I've owned. Maybe the flap rattles some when it switches over? The duct is on that side of the car, and it happens at the right RPM.

PhotoMunkey

Let's look at what we know...
1. Does it when car is hot.
2. Does it at high rpm when all injectors are firing
3. Does it when the engine is loaded and accelerating
4. Sounds like paper crackling when wadded up

I don't own and RX-8, so I can't try this, but what side of the engine does the exhaust exit? I'm placing my bet that unburned fuel vapor inside of the red-hot exhaust manifold is detonating. Fuel takes time to burn, and perhaps Mazda's still dumping in a bit too much for the rotor's duration. When the rotor uncovers the exhaust port, the unburnt fuel "fires" again into the exhaust, creating an accoustic "slap".

If the car also has a knock sensor "listening" for detonation, it might be hearing some of this and occasionally setting a CEL light on and off. Also that "misfire" could be the engine sensing that, while the exhaust port is open, when the mix accidentally fires again, it causes a bounce against the rotor, making the CPU believe there was a misfire. Place a quick-light cat high up in the exhaust stream, close to the ports, and I'm damn sure it'll fire any fuel vapor like a gunshot... In this case it just does it between 6000 and 8000 RPM like a machine gun.

Any other thoughts?

We all KNOW that Mazda's pumping in too much fuel... they always have, hence the need to move the exhaust ports to the side

PhotoMunkey

One more thought as to why you hear it the first time it's floored and perhaps not the second. If the CPU is set to balance the AF ratio based on the O2 sensor reading, perhaps it's "relearning the fuel curve" for that RPM. The next time you floor it, the CPU has a history to look at, and it balances the fuel, either from too rich (popping in the exhaust) to too lean (detonating in the cylinder) much faster, or simply has it nailed perfectly by then. Normally a CPU has a WOT (wide open throttle) fuel and timing map based on the air sensor, the throttle position, and the RPM because an O2 sensor can't read fast enough. It can only tell you what the AF should have been. If the map isn't right (and air density at your altitude would play a HUGE factor at 7500-8500 RPM) the CPU will happily go on over, or under fueling the car, based on that particular map, until another sensor tells it the CPU to change.

rollerbldes

Now that I think about it.. I think I have this too. 2005 AT.