rattling/vibrating around 1800 or 1900 rpm while accelleratgi fwd not stationary rev

dsc888

Member
:
2021 CX-9 GT
Hey Guys,

It's been a while since I posted to this thread but I can safely say that my issue is finally gone. I've had my 9 for almost 2 years and have about 12k on the odometer. The droning/buzzing at 1800 RPM bugged me for quite some time along with engine knocking on acceleration when the engine was warm.

Then helbigtw posted about Seafoam due to his cold engine knock. I've used it before in my lawnmower and in my other cars with good effect in the gas. I decided to run 2 cans of the stuff. I put 2/3 of it in my gas and 1/3 of it in my oil (crankcase). My warn engine knock is completely gone. And the droning cannot be detected at all. It took about 500 miles of driving to realize the benefits. I have no idea what in the Seafoam fixed it. Perhaps I had excessive carbon buildup. Maybe I had sticky valvetrain. I am not an engineer so your guess is as good as mine.

But I will note that I've started running 89 octane instead of 87. Our engine is too high compression in my opinion to get away with just 87. Cost difference is about 10 cents at the pump which is not that much money in the whole scheme of things.

I'm going to have my oil change soon so I will get rid of the Seafoam in short order. I'll post back here if my issues return.
 

dsc888

Member
:
2021 CX-9 GT
I have 4000 miles on mine and recently when the vehicle shifts from 3rd to 4th and the rpms fall to 1750 the exhaust kinda resonates and rattles like a lawn mower or weed trimmer. If I climb a hill around 25 mph at that rpm it continues until the engine rpm is more than 2000 rpms. My four year old exclaimed one day that it sounded like a lawn mower. This just started. I thought I was crazy.

Hmmm. That is interesting. Did you talk to the dealer about the issue? Perhaps an exhaust component needs to be secured or replaced. Hope you get it fixed.
 

GT500andCX9

Member
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2009 Mazda CX9 Luxury, 2008 Ford Shelby GT500
That's funny. I have the exact same problem, coming from the front left it sounds like. It's very annoying, and seems to disappear after 5 miles or so.

2009 CX9 luxury, 35k miles.
 

fireboy92k

Member
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2010 Mazda CX-9 Touring
Same here on a 2010 FWD

yes when it warms up it goes oway its less noticeble on a warmer day.

Live in Florida and have the same problem described here. It doesn't seem to result in a lack of power, just a strange humming rattle at low RPM while moving. Will not make it when tranny is in P, N or D and the car is stationary, only when moving under light accelerator application.

Seems to go away as it warms up.

Nobody has found out what this is? (cryhard)
 

helbigtw

T-Rav
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PA
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08 CX-9 GT FWD
Did you see the M Tip that I posted on page 1 of this thread?.
I don't know if that applies to 2010 model or not.
 

fireboy92k

Member
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2010 Mazda CX-9 Touring
Did you see the M Tip that I posted on page 1 of this thread?.
I don't know if that applies to 2010 model or not.

Yep, just hadn't seen anyone else post that they did it and that it fixed it. Lots of others about running Seafoam and higher octane fuel (neither of which I've tried either).

So wasn't sure. It honestly sounds like the 318 Chrysler that was in the van my dad had when I was a kid. LOL
 

Racerflash

Member
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2008 Mazda CX-9
Thank you, thank you, thank you! This is why I love car forums! My wife's 2008 CX-9 with 99,500 miles has been great since new! No problems and repairs except tires and brakes. But, it's been having this annoying vibrating and buzzing sound since right after the warranty expired. The dealer wanted to open up the motor, other mechanics thought it was an exhaust shield, still others stated I had valve train or timing chain problems. The noise had gotten even worse recently so I decided to hit the forums. This simple fix of adding a nut to the firewall/brake booster screw has 100% fixed this problem!

Thanks again and Merry Christmas to all!
Bob "Flash" Gordon
 
Did everyone confirm that adding the nut to the firewall solved these issues?

My wife's 2012 Cx-9 with 84k miles has the following:
1)Rev up on cold starts (exhaust sounds louder than before and sounds higher RPM)
2)SOme humming rattling when cold on while turning or going slow
3)The rattle/harshness at 1800-2000 RPMS

I've explored the following:
1)Checked all exhaust coverings
2)Checked all intake connections
3)Added the extra nut to the brakeline bracket
4)Today I just got the brake booster replaced under warranty

Any help or if you can point me to another thread that spoke of this issue I'd be extremely appreciative.
 
:
2011 CX-9 bose+sunroof, crystal white pearl
hello all, here is another one with exact same problem!

So far I tried with bolt exchange, checking brakes, exhaust heat shield, changing PTU and rear differential oil, .... but buzzing noise at around 2k RPM is still here.
timing chain is all OK as well.

I have 2011 CX9 GT AWD

I noticed that when i hear that sound if i gently press e-brake it will stop, then i tried to tighten e-brake a bit and it helped but temporarly because noise started again and I don't want to overtight the brakes.
BTW: I noticed that sometimes I can hear that sound although i have removed my foot from gas pedal completely (sometimes when going downhill) - in this case sound is quieter but I can hear it.

I have two suspects that I still didn't check:
1) exhaust silencer (it is possible that silencer resonates at specific RPMs sometimes)
2) e-break spring that I didn't check yet (spring close to the brake shoe in rear discs)

If someone managed to resolve this bussing noise I would be very thankful if you can share details...


Thanks to all

have found this to check (still haven't had time for it)
https://mazda.oemdtc.com/678/unusual-rattlebuzzing-noise-from-exhaust-2010-2015-mazda-cx-9
 
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2008 Mazda CX-9 Touring FWD . 2014 CX-5 GT FWD
I had a rattle noise coming from the top passenger side of engine that was noticeable under load around 2k rpm. It turned out to be bad VVT actuator that I replaced while swapping out the water pump. (see my thread for DIY)

If you haven't swapped out the infamous pump and are above 70k miles, you might consider adding VVTs to your parts list for that job. Eventually a bad VVT will likely throw a code.

I would not go through all that trouble just for a rattle though, so exhaust all other options first.
 
Thanks for the replies, we are starting to get frustrated with the situation getting worse.

I'll check out the pre resonator first and then see if I can isolate the VVT actuator. I wasn't aware of the waterpump issues, so I'll do some research on those.

Thanks again
 

MrMazDuh

Member
:
cx9
Thank you, thank you, thank you! This is why I love car forums! My wife's 2008 CX-9 with 99,500 miles has been great since new! No problems and repairs except tires and brakes. But, it's been having this annoying vibrating and buzzing sound since right after the warranty expired. The dealer wanted to open up the motor, other mechanics thought it was an exhaust shield, still others stated I had valve train or timing chain problems. The noise had gotten even worse recently so I decided to hit the forums. This simple fix of adding a nut to the firewall/brake booster screw has 100% fixed this problem!

Thanks again and Merry Christmas to all!
Bob "Flash" Gordon

where are you guys adding this nut? does someone have a picture?
 
I had the same problem when the car had a load on it at low speed. The muffler has a soft spot in it on the bottom of main chamber. I used a large hose clamp all the way around muffler with a piece of metal squeezed up into soft spot to depress it and take away the vibration.

I know this may sound crazy, but it worked for me. My dad owns a repair garage. I put the car on the hoist and walked underneath with a rubber mallet and started tapping on different areas. When I got to the muffler and tapped, I heard it. There was a soft spot in the muffler.

Scott
 

helbigtw

T-Rav
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PA
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08 CX-9 GT FWD
When I get home I will take a photo and upload it on here. I fixed it many years ago. Very very easy...it was a really noisy rattling under load around 1800rpm or so. It was a component bolted to the cowl that needed a nut and a washer I think. It made a huuge difference. The cx9 does have that weird trans noise in first gear under light accelleration but that is completely normal.
 

helbigtw

T-Rav
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PA
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08 CX-9 GT FWD
Ok here's the info on how I fixed it many years ago.
Simple fix. See below. This was a night a day difference for me.
Amateur tip: you don't have to remove the battery.
I hope this is able to help someone!


<img src="https://i.ibb.co/h9W6BPX/1.jpg" alt="" width="1630" height="917" data-load="full" style="">

<img src="https://i.ibb.co/kgB3hy8/2.jpg" alt="" width="1630" height="917" data-load="full" style="">

<img src="https://i.ibb.co/27TJkqx/3.jpg" alt="" width="799" height="655" data-load="full" style="">
 
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