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Intermittent engine loud/grumbling engine noise - going crazy trying to figure out what's up!

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Felix_52

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Discussion starter · #1 ·
Hi everyone.

I'm experiencing an intermittent issue with my 2023 Rav4 hybrid where the engine makes loud noise/rumbling at low RPM. The vibrations can be felt in the gas pedal when this occurs.

The noise can be typically be reproduced while feathering the gas/cruising around 40 or 60. Can also be reproduced by feathering the gas while going very slow ~10 (starting and stopping in a parking lot for example).

Videos:
1) prolonged recording of the sound, taken going ~10kmph
2) brief recording showing the noise while accelerating
3) prolonged recording of sound, taken going ~40kmph

Video 1: car audio 1.mp4
Video 2: car audio 2.mp4
Video 3: car audio 3.mp4

Does anyone have any insight into what this might be? I've taken it to the dealership 3 times and they agree something is up based on the videos, but they haven't been able to solve it.

Any ideas are appreciated!
 
#2 ·
Noise diagnosis is hard in your case because the rumble is NOT constant and only occurs at low speed/low RPMs. I will give some suggestions about the rumbling noise relating to the gas/ICE engine. I will leave it to others to give suggestions relating to the hybrid systems and eCVT. There are two main diagnosis for rumbling noises like in your audios: 1. an exhaust leak, 2. an air/fuel mixture imbalance. If the gasket between the primary catalytic converter (which is up near the firewall welded to the end of the exhaust headers) and down pipe has failed or there is a pinhole or hairline crack in the exhaust headers it could make that sort of noise--but I would expect it to get louder when the ICE is running and accelerating at higher RPMs and stay constant. An A/F ratio imbalance could make an intermittent rumble. It could be caused by many things. Your rumble might be caused by the top of the air box not being clipped down properly or the big tube going to the throttle body being loose--you could be hearing an air intake roar or rumble at certain RPMs and engine loads. I'd want the dealer service tech to run a Techstream scan for all DTC codes. This is always the first, basic step for any engine issue.
 

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Discussion starter · #3 ·
Thank you for this, it's actually very helpful.

The noise only occurs when the ICE is running so I'd assume what you've written here applies to my engine as well, despite it being part of the hybrid system.

Re the techsteam, would that be able to pull anything useful if no errors (eg. check engine light) and being displayed on the dash?

My next step will be driving with a tech to show them the noise in person. Would I want some diagnostic tool plugged in while I'm driving?

Thanks again!
 
#4 ·
Felix_52 said:
Re the techsteam, would that be able to pull anything useful if no errors (eg. check engine light) and being displayed on the dash?

My next step will be driving with a tech to show them the noise in person. Would I want some diagnostic tool plugged in while I'm driving?
Click to expand...
There are MANY gas engine and hybrid system problems that do NOT light up the CEL. In RAVs, sometimes you get warning messages on the MID instead of trouble lights, sometimes no warnings or lights even if there are DTCs. Techstream finds ALL DTC codes in every module (computers--I think 32 of them in RAV4s). The Techstream or an aftermarket, advanced, expensive scan tool can indeed be plugged into the OBD2 port while driving for diagnosis--though that is usually not necessary. If the problem is something like a cracked exhaust manifold the Techstream may find a code for the air/fuel mixture being incorrect; or it will find a problem in the long term or short term fuel trims, or in the downstream (after catalytic converter) O2 sensor. Some hardware issues--like wheel bearings, CV joint--that can make rumbling noises are not diagnosed electronically by Techstream. Those things are diagnosed by an experienced mechanic listening while riding in the car and following up with hands on physical tests (spinning the wheels with the car on a lift for example.)
 
Discussion starter · #6 ·
No issue with the snow/damage. We first started noticing the noise in the fall.

Hard to say if I can recreate it in neutral, it usually happens while I'm in motion. I have a video of me going up and down the revs while in neutral and you can hear the tone shift into something deeper.

Video
 
#7 ·
There are moments when you can achieve those speeds with propulsion done by the battery only if you look at the power meter. This would be key to rule out the engine and the exhaust and to focus on the driveline if the noise is present without the engine running. I assume the engine has to be involved for the noise then. Tough one for sure. Perhaps, a pro needs to use chassis ears or something.
 
Discussion starter · #8 ·
14v6 said:
There are moments when you can achieve those speeds with propulsion done by the battery only if you look at the power meter. This would be key to rule out the engine and the exhaust and to focus on the driveline if the noise is present without the engine running. I assume the engine has to be involved for the noise then. Tough one for sure. Perhaps, a pro needs to use chassis ears or something.
Click to expand...
I see what you mean. It's 100% when the ICE is running. The car is whisper quiet when it's using the EV.
 
#9 ·
Felix_52 said:
I see what you mean. It's 100% when the ICE is running. The car is whisper quiet when it's using the EV.
Click to expand...
After listening to your last video, that noise sounds like more of a hum than a rumble and the hum increases and rises in pitch as the ICE RPMs increase. If your RAV was a gas model I would guess it's the rubber drive belt or idler pulley, but in your HYBRID you do NOT have these parts.
 
Discussion starter · #10 ·
Tazio Nuvolari said:
After listening to your last video, that noise sounds like more of a hum than a rumble and the hum increases and rises in pitch as the ICE RPMs increase. If your RAV was a gas model I would guess it's the rubber drive belt or idler pulley, but in your HYBRID you do NOT have these parts.
Click to expand...
Agreed. I'm not sure if the revving of the engine is the best representation of the issue since I mostly notice it while cruising and it is more of a rumble when that occurs.

I just noticed the change in pitch with revving and assumed it was related.

Videos 1 and 3 in the initial post are the best examples of what it normally sounds like when it occurs.
 
#11 ·
Felix_52 said:
Agreed. I'm not sure if the revving of the engine is the best representation of the issue since I mostly notice it while cruising and it is more of a rumble when that occurs.
Click to expand...
I'm glad you revved the engine!! With the car stationary-not moving-that HELPS diagnosis. You can now forget about driveline or chassis noises. It is definitely NOT wheel bearings, CV joints and so on causing the noise because they were not moving with the car stationary. The noise has to be in the engine or eCVT. Can't some knowledgeable hybrid fanatics respond to this thread to help OP if the issue is in the eCVT? Where are you guys?
 
#12 ·
Tazio Nuvolari said:
The noise has to be in the engine or eCVT. Can't some knowledgeable hybrid fanatics respond to this thread to help OP if the issue is in the eCVT? Where are you guys?
Click to expand...
On the road, noise sounds, to me, to be road noise. Some tire tread designs can make that noise depending on the surface. Smooth asphalt is usually the quietest, concrete is next, and some course asphalt, like they put in front of my house last summer, can be very noisy. Even at slow speed pulling into my driveway, can make lots of noise.

If car is not moving, I would suspect the direct injectors. They can make quite a bit of noise that others on the forum have complained about from time to time. OP, try opening the hood and try to locate the source of the sound.

I doubt the eCVT would make any noise at any time, especially when the car is not moving. With the gas engine running, the planet gears and the sun gear in the planetary gear set would be turning, but will not make noise. If any noise were to be made by them, it would be a gear whine, not the rumble the OP is hearing.
 
#13 ·
The Toyota D4S fuel injection can make the engine intermittently clattery, almost diesel-like. When it switches from port injection to direct injection, it gets noisy. It almost sounds like something is wrong, but it’s normal. A friend‘s new Tacoma does the same thing.
Not sure this is what you’re experiencing, but it could be.
 
Discussion starter · #15 ·
nels0300 said:
The Toyota D4S fuel injection can make the engine intermittently clattery, almost diesel-like. When it switches from port injection to direct injection, it gets noisy. It almost sounds like something is wrong, but it’s normal. A friend‘s new Tacoma does the same thing.
Not sure this is what you’re experiencing, but it could be.
Click to expand...
Not sure if this is quite the same. The car never made the noise for the first 10,000km or so, it's just over the past few months where it started
 
#16 ·
Tazio Nuvolari said:
I'm glad you revved the engine!! With the car stationary-not moving-that HELPS diagnosis. You can now forget about driveline or chassis noises. It is definitely NOT wheel bearings, CV joints and so on causing the noise because they were not moving with the car stationary. The noise has to be in the engine or eCVT. Can't some knowledgeable hybrid fanatics respond to this thread to help OP if the issue is in the eCVT? Where are you guys?
Click to expand...
I think it is okay not to say anything if you don’t know. There is no shame in that. But to make wild theories when you have no clue is not so cool in my book.
 
Discussion starter · #17 · (Edited)
FKHeath said:
On the road, noise sounds, to me, to be road noise. Some tire tread designs can make that noise depending on the surface. Smooth asphalt is usually the quietest, concrete is next, and some course asphalt, like they put in front of my house last summer, can be very noisy. Even at slow speed pulling into my driveway, can make lots of noise.

If car is not moving, I would suspect the direct injectors. They can make quite a bit of noise that others on the forum have complained about from time to time. OP, try opening the hood and try to locate the source of the sound.

I doubt the eCVT would make any noise at any time, especially when the car is not moving. With the gas engine running, the planet gears and the sun gear in the planetary gear set would be turning, but will not make noise. If any noise were to be made by them, it would be a gear whine, not the rumble the OP is hearing.
Click to expand...
Haha. Noooo definitely not road noise. It's not my first time on the road ;)

But in all seriousness, this is a noise that had just popped up over the past few months. I've had the car for about a year now as a daily driver so I'm pretty familiar with all the regular noises

In video 3 if you can focus on the rough engine noise you'll notice that it stops about half way throughout then it starts back up in a sort of sputtering fashion. That all happened on a straight smooth road. The noise happened when I was feathering the gas, and went away when I pressed a teensy bit harder. I can also feel the vibrations of the noise in the gas pedal when it happens.

Aside from the weird engine noise, I find the car is pretty quiet in most circumstances.

Edit: should also mention that the noise is coming from the engine bay, not the floor of the car.
 
#19 ·
nels0300 said:
The Toyota D4S fuel injection can make the engine intermittently clattery, almost diesel-like. When it switches from port injection to direct injection, it gets noisy. It almost sounds like something is wrong, but it’s normal. A friend‘s new Tacoma does the same thing.
Not sure this is what you’re experiencing, but it could be.
Click to expand...
Felix_52 said:
In video 3 if you can focus on the rough engine noise you'll notice that it stops about half way throughout then it starts back up in a sort of sputtering fashion. That all happened on a straight smooth road. The noise happened when I was feathering the gas, and went away when I pressed a teensy bit harder. I can also feel the vibrations of the noise in the gas pedal when it happens.
Click to expand...
Sounds more and more like the direct injectors as nels says.
 
#20 ·
FKHeath said:
Sounds more and more like the direct injectors as nels says.
Click to expand...
NO it is NOT direct injectors! They and the high pressure fuel pump mounted on the engine make clattering, clicking noises. If you listen to the OPs audios and videos it is a low continuous hum or rumble--not a clatter. Also as OP says he's had the RAV for a year and he's familiar with the normal noises and that hum is a new and different noise.
 
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