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Discussion Starter #1
Hi guys,

What an excellent forum this is!

I just picked up an 09 Rav4 CV FWD. 168000kms on the clock. Full service history.

Last service was around 8000kms ago.

Last night was the first time driving on very smooth roads, so I could hear every noise from the car in detail.

When accelerating, from about 35-40km/h I can hear a woo woo woo or wah wah wah noise. As I accelerate, the frequency increases till it is a solid noise at around 60-70km/h. What's strange is that the noise disappears if I back off the accelerator.

I thought if it was bearing or tires, the noise would be constant regardless of acceleration. Is that correct?

I'm going check the diff oil.

What would you suggest in terms or troubleshooting?

I could provide a high quality recording of the noise if anyone thinks that could be helpful.

Many thanks,
B
 

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Welcome! Has the engine air intake been modified from the OEM spec? Also suggest checking the transmission fluid level and appearance.
 
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Discussion Starter #3
Hi there,

No modification to air filter.

Checked the transmission fluid when I bought it. Slightly discoloured, but not burned. Have done the first of three drain and fills with new ATF.

Any other suggestions?

Thanks,
B
 

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Hello bermanc2,

My vehicle is a 2008 AWD at 149000 km and I get a similar noise but at a lower speed, 25 mph. (35-40 kmh). I had the transmission checked by three shops and it's all good, they said. And it does run nicely, so..

The best suggestion I have had so far was the differential, where the shaft may have a micro dent in it, but those mechanics all assured me that this does not break and it is good for the rest of the vehicle's life. I am still trying to find out if that is adjustable in some way.

So by all means get the oil level checked.
 

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Discussion Starter #5
Hi and thanks for the info! Most interesting.

I will check the diff oil level and report back.

Just hope it's nothing serious.
 

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Discussion Starter #6
Well I finally got round to checking the oil levels in the front and back diff and they are fine, and the oil is clean. I have no idea now.

Could anyone suggest where to go from here?

Thanks!
 

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I have just purchased a 2010 model Rav4 with 150,000km with the exact same issue you are describing. I have it booked in for a statutory warranty claim, so I will let you know what I find out.

Do you have any answers yet?
 

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Discussion Starter #8
Hi Maikiw,

No answers yet. I don't think it's tires or bearings.

I eagerly await the results of your warranty claim.

Hopefully the answer to your problem is the answer to my problem.

Thanks,
B
 

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1999 Toyota RAV4 with 3MZ-FE 6 cylinder engine, camo wrap, OME lift, heavily modded
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Check the knock sensor it can make a sound like you are describing. If you have the 1MZFE engine it is very susceptible to knock sensor problems. If it is the knock sensor and you drive the car you will cause damage to the engine.
 
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I also have a similar problem (posted in a similar post here). The sound, however, starts as soon I start accelerating up to about 45 mph then it stops. No other issues whatsoever. I have about 95K miles on mine (09/V6-4WD-limited). I'm yet to have the transmission and fluid checked, which I plan to do this week.
 

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1999 Toyota RAV4 with 3MZ-FE 6 cylinder engine, camo wrap, OME lift, heavily modded
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Everyone posting a similar problem here, please list your engine.

As I stated earlier the knock sensor can make an engine make noises like this. The big issue is that if it is the knock sensor, you will cause engine damage if you continue to run it. A v6 will usually have 2 knock sensors.
 
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Everyone posting a similar problem here, please list your engine.

As I stated earlier the knock sensor can make an engine make noises like this. The big issue is that if it is the knock sensor, you will cause engine damage if you continue to run it. A v6 will usually have 2 knock sensors.
But wouldn't that trigger the engine light and generate an OBD code?
 

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1999 Toyota RAV4 with 3MZ-FE 6 cylinder engine, camo wrap, OME lift, heavily modded
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But wouldn't that trigger the engine light and generate an OBD code?
Yes it usually will throw a code, but don't rely on it, the more you know about the OBDII system the more you come to understand it isn't always effective and at best the codes can be several if not dozens of things. Proper diagnostics is important rather than remove and replace parts until you get it right unless you have lots of time and deep pockets. I'm not saying it is definitely the knock sensor, after all I'm trying to diagnose a problem with vehicles that I haven't even seen or heard, much less driven. All I am trying to do is point out possibilities that are often overlooked by the so called stealerships and remove and replace mechanics.

The following describes the knock sensor problem better.

Your vehicle's engine is controlled by various sensors responsible for regulating important functions, such as fuel management, emissions, ignition timing and transmission shifting. One sensor in particular, called the knock sensor, acts as a sophisticated listening device in the engine. It detects any engine noises caused by detonation -- when fuel explodes in an engine's cylinder-- and adjusts ignition timing accordingly. If the knock sensor malfunctions, detonation is not properly regulated and major engine damage can occur. Recognizing the symptoms of a bad knock sensor and replacing it, may help you avoid costly repairs

Usually a bad knock sensor will trigger the "check engine" light to flash on your vehicle's dashboard. Sometimes, using cheap gasoline causes detonation and triggers the power train module -- the engine's main control board -- to wrongly diagnose the knock sensor and send a false malfunction message via a check engine light. Try filling your vehicle with a higher grade of gasoline, and if the light is still flashing, consult with a mechanic.

I've heard the noise made by an engine with a bad sensor and it can be described as a whumping or thumping noise, it usually is often more pronounced when the engine is under load. Some engines cannot use 87 octane fuel reliably although the owner's manual says you can and you need a 91 or better octane fuel to keep engine knock from being a problem. The 1MZ-FE engines are very susceptible to this problem and it's been well documented.

Noises
If the knock sensor is not working properly, you will likely hear sounds emitting from the engine. You may hear loud thumping noises that become louder over time. The noise is a result of fuel and air igniting inside the cylinder, instead of reaching the point of combustion.

Other Symptoms
There are several other symptoms indicative of a knock sensor problem. The vehicle will often shake or vibrate and misfire when the engine is started. The engine may emit strong exhaust and burning smells due to the detonation in the cylinders. Fuel economy is often affected, causing the vehicle to burn more gas than usual and requiring frequent fuel replenishment. Also, your vehicle may display acceleration problems, such as dragging, hesitation or jerking from the engine during speed increases.

Ref: https://itstillruns.com/symptoms-bad-knock-sensor-7488824.html
 

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Yes it usually will throw a code, but don't rely on it, the more you know about the OBDII system the more you come to understand it isn't always effective and at best the codes can be several if not dozens of things. Proper diagnostics is important rather than remove and replace parts until you get it right unless you have lots of time and deep pockets. I'm not saying it is definitely the knock sensor, after all I'm trying to diagnose a problem with vehicles that I haven't even seen or heard, much less driven. All I am trying to do is point out possibilities that are often overlooked by the so called stealerships and remove and replace mechanics.

The following describes the knock sensor problem better.

Your vehicle's engine is controlled by various sensors responsible for regulating important functions, such as fuel management, emissions, ignition timing and transmission shifting. One sensor in particular, called the knock sensor, acts as a sophisticated listening device in the engine. It detects any engine noises caused by detonation -- when fuel explodes in an engine's cylinder-- and adjusts ignition timing accordingly. If the knock sensor malfunctions, detonation is not properly regulated and major engine damage can occur. Recognizing the symptoms of a bad knock sensor and replacing it, may help you avoid costly repairs

Usually a bad knock sensor will trigger the "check engine" light to flash on your vehicle's dashboard. Sometimes, using cheap gasoline causes detonation and triggers the power train module -- the engine's main control board -- to wrongly diagnose the knock sensor and send a false malfunction message via a check engine light. Try filling your vehicle with a higher grade of gasoline, and if the light is still flashing, consult with a mechanic.

I've heard the noise made by an engine with a bad sensor and it can be described as a whumping or thumping noise, it usually is often more pronounced when the engine is under load. Some engines cannot use 87 octane fuel reliably although the owner's manual says you can and you need a 91 or better octane fuel to keep engine knock from being a problem. The 1MZ-FE engines are very susceptible to this problem and it's been well documented.

Noises
If the knock sensor is not working properly, you will likely hear sounds emitting from the engine. You may hear loud thumping noises that become louder over time. The noise is a result of fuel and air igniting inside the cylinder, instead of reaching the point of combustion.

Other Symptoms
There are several other symptoms indicative of a knock sensor problem. The vehicle will often shake or vibrate and misfire when the engine is started. The engine may emit strong exhaust and burning smells due to the detonation in the cylinders. Fuel economy is often affected, causing the vehicle to burn more gas than usual and requiring frequent fuel replenishment. Also, your vehicle may display acceleration problems, such as dragging, hesitation or jerking from the engine during speed increases.

Ref: https://itstillruns.com/symptoms-bad-knock-sensor-7488824.html
Thanks for the thorough explanation for those of us who are not so mechanically-savvy. In my case, it's only the sound at low speeds up to 45 mph, everything else seem to work just fine and I haven't noticed any of the symptoms you described above. Having said that, I will pay closer attention and report back with anything that's unusual.
 

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...I just picked up an 09 Rav4 CV FWD. 168000kms on the clock. Full service history.

... When accelerating, from about 35-40km/h I can hear a woo woo woo or wah wah wah noise. As I accelerate, the frequency increases till it is a solid noise at around 60-70km/h. What's strange is that the noise disappears if I back off the accelerator.

...What would you suggest in terms or troubleshooting?

...I could provide a high quality recording of the noise if anyone thinks that could be helpful.
Since there are no RAV4 CV models in the USA, I'll guess you are in Australia or possible Europe. (Helps to complete your profile.) The 2009 Aussie RAV probably has the 2.4L engine, and the 2009 USA RAV has the improved 2.5L, but I think the 4-speed tranny is the same on the base models .

The noise is likely a tranny noise. Fairly common with a lot of Toyotas., you get answers from "they all do that" to you should replace the tranny. The noise ranges from barely perceptilble (in my 4-cyl 09 RAV) to somewhat noticable (in my friend's 4-cyl '11 RAV). I call it a "whirling" noise, but I suppose it could be a woo woo or a wah wah, it is harmonic. My mechanic said keep an eye on it, her mechanic said "they all do that," You have to have a good ear to hear it, it starts under light acceleration at about 25 mph and increases until around 45 mph where it might still be there, but lost in road noise.

Put it on a lift, have the mechanic listen with a stethoscope while running under light acceleration, checking the tranny and the rear differential, if your FWD even has one. Then you'll know for sure.

Yes, do make a sound recording.

Of note, the V6 has a TSB on their 5-speed tranny, and some have had it replaced under warranty. It is defined more as a "whine" than our 4-speed whirly woo woo wah wah. I don't think there is a TSB for our 4-speed. Either way, you either learn to live with it or replace the tranny.
 

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Yes a sound recording would be the best. I bought a mechanic's stethoscope a few days ago and I am going to set it up for recording my own 2008's woo woo sound. On a side note, my wife's 2011 has started a very faint woo woo too.

Here's another piece of info to consider, it's in T-SB-0001-11 January 4, 2011, and is titled "Transaxle Rattle Noise between 25 - 35 MPH." You can get that pdf download easily using Google, it's somewhere on this site.

They describe the fix as "Recalibrate ECM (PCM) Engine", which involves the dealership using "TIS Techsctream" (at the dealer that's really really expensive) or if you are adventurous, eBay or Amazon's TIS Techstream clone (under $30).

Maybe the latter procedure would void your Toyota warranty, but hey, mine ran out a while back. So I am looking for users who are experienced with that software, hoping that they can tell me about its pros and cons.
 

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Discussion Starter #18
Hi,

I am in Australia and have the 2AZ-FE engine. The car does have a front and rear differential.

I wouldn't describe the noise at all like a whump or thump. It is fairly loud on smooth roads and not audible on rough roads. The car has a slightly noisier idle than I would like, but I haven't looked properly into that yet. Fuel consumption is around 11-12 L/100km around town which is slightly higher than I'd like but not excessive from what I've read.

I will have to make a recording in the next few days and post it. And I will have a look at the knock sensor.

Thanks for the replies. I hope we can all resolve our issues!
 

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Discussion Starter #19
Yes a sound recording would be the best. I bought a mechanic's stethoscope a few days ago and I am going to set it up for recording my own 2008's woo woo sound. On a side note, my wife's 2011 has started a very faint woo woo too.

Here's another piece of info to consider, it's in T-SB-0001-11 January 4, 2011, and is titled "Transaxle Rattle Noise between 25 - 35 MPH." You can get that pdf download easily using Google, it's somewhere on this site.

They describe the fix as "Recalibrate ECM (PCM) Engine", which involves the dealership using "TIS Techsctream" (at the dealer that's really really expensive) or if you are adventurous, eBay or Amazon's TIS Techstream clone (under $30).

Maybe the latter procedure would void your Toyota warranty, but hey, mine ran out a while back. So I am looking for users who are experienced with that software, hoping that they can tell me about its pros and cons.
I'm going to get Techstream up and running on my Laptop in the next few days. Will report back with details.
 

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Hi Bermanc2,

Where abouts in Australia are you? I just had the warranty check done and turns out it was transmission bearings. I've got it booked in for next friday to fix. Fingers crossed the noise disappears. The tech who looked at has seen it dozens of times so he's pretty sure its transmission.

Hope the helps.

Cheers.
 
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