I see plenty of previous posts on "Engine Clattering "noise, but I could not determin anything close to a reason for it - So with applogies for re-starting this subject, here is what I recently experienced - any theories on what it could be will be greatly appreciated by myself and the RX8 Tech who can't figure it out either.

2004 RX8 AT, with 19,000 miles.

Yesterday at about 5000 rpm, 2nd gear my passenger and I both heard a loud, fast "Rattling" sound. To my ear it sounded just like a worn bearing running well over it's design speed (I know it's not that, just trying to describe the sound).

Back off the throttle and sound went away, I think I alos lost some power while this sound was happening, but I can't be absolutely sure.

Anyway, continued on our 200 mile journey and as long as I kept below 5000 rpm all was OK for quite a while, then the sound came back again, this time at lower rpms of 2000 - the noise was unmistakable, I really thought my engine was falling apart.
Lifted the hood to see if anything obvious, at idle no noise, with passenger moving engine speed up to 2500 I heard the noise, and it seemed to be coming from the two aluminum tubes entering the engine left side looking into the hood.

Nursed it home, drained the oil expecting to see metal parts - nothing, oil bucket was a clean as a whistle.

Took it to my local Mazda mechanic next day, on the way I tried to re-produce the clattering noise, I could not get it to make the noise that was so ewasy to reproduce the day befoer !!! - doesn't that make you mad !!

Mechanic looked it over test drove it, could not get it to make the noise, checked engine codes, re-calls, service bulletins etc - Nothing.

Anyone have a clue about what might be wrong so I can give my Mazda tech some idea about what to look for?

 

Is this a double post?

See this thread you started: https://www.rx8club.com/showthread.php?t=166421


You can delete either this thread or the other one by looking at the "Thread Tools" drop down at the top right side; then click on "Delete Thread"

 

What octane fuel are you using? reg-87 mid-89 or prem-91?

 

It looks like a double thread, I don't know why, I only started it once to my knowledge.
Answer to fuel question; I use mid grade and have done for 4 years without problem.
Also, the sound I am hearing is very different from what I know as Ping or engine knock that is heard in piston engines running low octane fuel.
Does engine "Knock" sound that different in a rotary ?

 

Very different - it has been compared to "marbles in a coffee-can"....

S

 

Some times known as "MIAC" Marbles In A Can. Here is some info...


https://www.rx8club.com/showthread.p...highlight=MIAC

 

So what we have so far is either low grade fuel or air in the coolant.
1) Fuel, well the same fuel is in the tank today as yesterday, yet we can't re-produce the Rattling. Doesn't sound like it's the fuel.

2) Air in the coolant, maybe, how does one find out if this is the case and how to remove the air ?

3) One suggestion was to by-pass the air intake water heating pipes. I don't see the logic in this, anyone care to clarify this theory?

I am still have trouble believing it is any of these possibilities - the sound we heard yesterday was quite dramatic..

I have one other thought - there must be some kind of air control valves in the intake, could they be mechanically loose or have weak springs etc.

Any other thoughts or diagnostics to try.

 

I hope it's not Detonation because it is very bad for the Rotary. Try prem-fuel and if it goes away then there you are.

 

Here is another theory on the engine rattling noise up for comments -
Water in the oil, https://www.rx8club.com/images/smilies/Eyecrazy.gif.

Maybe because the RX8 engine allows a significant amount of water to collect in the engine oil, there is "Cavitation" going on.
As a process engineer I know the sounds cavitation in pumps and valves can make, this engine rattling noise is quite similar in many respects.

For those who don't know about cavitation, the simple explaination is when a fluid turns into a vapor and then the vapor bubbles collapse very quickly in a confined place such as the inlet to a pump OR a rotary engine.
The water in the oil gets very hot and so would easily turn into a vapor at the slightest lowering of pressure which could occur within the rotating parts of the engine.

This might explain why I could not re-produce the Rattling noise when all I did was change the oil !!

Could the rotary "Gurus" please comment.

 

Do you have stock cat? If so unbolt and check it.

 

I can take the stock CAT off and check it, but if it were faulty wouldn't that show up as check-engine-light.

Could you explain what am I looking for and why this might contribute to the rattling noise.
By the way, still using same tank of gas and no signs of the rattling noise heard two days ago. All I have done is change the oil..

 

this same exact thing happens to me, i have a 07 A/T with 55k miles. this problem occurs when i have been driving a while and when the engine is the hottest. when i apply any acceleration there is a clattering noise (sounds exactly like birds chirping). i can never home in on the location of the sound because this only happens when in Drive, and just like Foamy says anything past 5k rpm there is a loud raspy/ rattling sound followed by a little bit of power lose.

in my opinion i think its the ssv trying to operate properly, but due to the intense heat, its not opening or operating right hints the loud clatter/ rasp noise at high rpm when it is supposed to actuate.

like i said tho this only happens when the engine is at its hottest or standard operating temp, otherwise it drives fine and smooth.

 

I would love a solution to this issue. I've been dealing with this for some time now and I'm losing it. 2006 6MT and same kinda thing, about 5k RPM and up, a God awful rattling sound like the engine is coming apart at the seams accompanied by power loss. Only happens under load with the engine hot. I have already replaced the SSV, the VDI, the APV valves, and verified the solenoids and APV motor are good. Valves all move freely, even hot (about 7 inches of vacuum applied for full activation). I'm running 91 octane fuel and verified today that the catalyst is fine, both via scanner and physical inspection. All new ignition coils, plus, and wires. Fresh oil. I'm at the point where I can only assume the damned apex seals are leaking compression at high RPM, but I'm really hoping that's not the case. Seems fine at idle and sometimes it'll actually come back to life when hot if it's run hard. No coolant in the oil either. Like I said, I've done everything I can think of and I'm stumped. Hope this is helpful info for any real gurus out there.

 

Bump to share since this thread is relatively new. I have the same (or similar issue): chirp on start up and throttle, raspy/rattly sound under load/acceleration. Engine runs smooth with a tiny dip around 7K. No issues getting to readline, no CEL, starts fine both hot and cold, but I do get awful city and hwy mpg. I plan to change oil and check the cat this weekend. Not sure what else to look for. Plugs? Ignition system has about 17k on it.

Hopefully someone that has experienced this and found a solution will share. I'm sure it could be many things, but the rasp in conjunction with the chirp seems like a pretty unique set of circumstances.

 

Update for those who might come across this issue at some point. I replaced the ignition system with BHR coils and NGK plugs, and I still have a slight chirp and rattle. The car does run better though. LOVE the coils.


I noticed the ring around my O2 sensor glowing prior to replacing the coils, inspected the front of the cat and saw no signs of damage, but I didn't have time to pull it all the way out. Tonight I will inspect it again after it warms up. Have a feeling the Cat is going bad. If the red ring of death reoccurs after replacing the coils, its time for a new cat.


Cheers.

 

Did anyone find out a solid solution to this issue? I have the same issue when above 5krpm, just wondering how to go about fixing it.

 

Did you find a solution to this problem?

 

So I'll throw my hat into the mix (even though I'm S2). This just started for me a couple days ago. Between 5500-7500 I have a clear rattling sound, which sometimes happens on a cold start as well. As the engine warms up at idle the sound goes away. I don't really feel any substantial loss of power, still goes to redline just fine.

I always pre-mix, always use premium, have fresh plugs with BHR ignition. Car has 115k miles, prior to this it's ran like a top for years.

Mine definitely sounds like its coming from the rear of the engine, towards the passenger side. It's a fluttering/clacking sound, changes frequency with the rpms. I'm hoping its just a motor mount, which would make sense (never changed mounts). The sound is right near where all three solenoid valves are on the back of the engine (SSV, VDI, Air Pump), so I'll have to pull the codes to see if any of those are the culprit. It could also be an exhaust leak at the header. I'll update this thread as I find out more.

 

I’ve had what seems to be the same issue. Rattling noise @5500+ rpm and noise speeds up with increased rpm. My guess/fear is that the apex seals are losing contact with the walls and the noise is from them reconnecting. Maybe the springs just aren’t doing their job at the higher rpms anymore? Again, it’s just a guess. The sound to me is a raspy sort of shickashickashicka noise. I haven’t put a lot of miles on it since my last oil change but it has been quite a while, so i’ll probably do that. Just curious if anyone’s solved their own rattle yet.

 

Any performance related issued or rattling noticed outside of the car?

It's either the MIAC (marbles in a can) rattle that comes from a catalytic converter that has some breakdown of the mesh or the SSV.

Run a Google search on this site to find many mentions of rattling sounds.