Sound When Accelerating

[Mikastef]

Dear all,

My YARIS is a 1000cc engine which drives 100km every days, for six days a week. It has an automatic gearbox. I am approaching 100,000km and I am quite proud to say that this yaris is a very reliable car indeed...it has never failed me ....for now....and I plan to make it go over 200,000km...hopefully ...

I am very very disciplined in servicing it every 8,500km and do a lot of preventive maintenance. I change all fluids in due time.

My daily trip consists of 50% highway driving and the rest, a mixture of traffic jam and normal driving .

But lately, I am starting to hear some strange sound upon pressing the accelerator pedal. The sounds characteristics are as follows

-It occurs at random...say 40% of the time....not every time!!
-I noticed that it occurs mostly when I am driving around 30-70km/hr, and it is more pronounced when I am overtaking a vehicle and pressing more on the pedal. It nearly never occurs (or I don't hear it) when I'm driving over 90km/hr..I think when I put some serious load on the car in the 30-70km/hr range that I can hear it mostly...for eg. When I'm driving on a hill, overtaking, just slowed down after a hump and then accelerating fast to speed up..

The degree of occurrence decrease at night...since perhaps there is no load on the car as the road is very clear and I can drive at ease (few stop and go)...it also never occured when I am going downhill.

-it seems to be a metallic sound (like pebbles shaking in a bottle lightly..or like a light metal rattling/hitting lightly against each other...)....

-I am still trying to record it but it occurs randomly and thus is quite difficult to record...

Once I get a good recording of it, I will post it.

-I feel that the sound occurs in the engine bay, in the driver side corner (where the water pump, accessory belt etc are found ). Sometimes my ears and mind plays me tricks and I feel it is at the back of the car


I have made some research online and some pple say that it may be due to

1. Heat shield which is loose -nope.i made a mechanic checked my heat shield and apparently it is good and not loose.

2. It relates to gas octane ratio ..- well I have changed fuel stations so many times. And it random occurrence makes it difficult to know for sure if it related to this problem.

3. Transmission problem - I pray that it is not.....!!!!!! But I don't get any gear shift problem. My transmission is smooth.

4. Loose Vacuum or dirty throttle - well I didn't check the loose vacuum yet.and some 30,000 km back I did make the mechanic cleaned the throttle.

5. Brake pad - i still have some brake pad left.

6. Axle or cv joints - nope. I don't have any problem when turning. My car is smooth when I'm turning.

7. Water pump -but it occurs mostly on acceleration...so how is it related to water pump??? And my car temperature seems ok..ranging around 85-95 degree. I plan to change the water pump when I reach 100,000km.

8. Bearing - wheel? Other bearing near the water pump?? I don't know..didn't check yet.

9. No error code either through OBD Scanner

10. Timing chain going bad- my god...this is going to cost a fortune to change ! I hope not..the car is still young...

Please help me...

I noticed that mechanic sometimes does not know your problem exactly...and it is up to us, the drivers that give the mechanic all the clues for a successful diagnostic. Else we run the risk of spending lots of time at the mechanic or, the car may get damaged eventually due to bad diagnostic

I have managed to record a bit of this sound... well it is a very faint sound alongside the engine sound.

Total time: six second.

https://www.dropbox.com/s/w3a7udwj35...044-2.mp3?dl=0

The strange sound basically appear first at 1 second, and then between 2.5 second to 3.5 second. you will hear that it is not the engine. And normally I get the sound more "INTENSE and Louder" than this recording. I mean, sometimes it is loud and continue for 2 - 5 second when accelerating.

Here it is rather faint and last less than one second...

(Basically, I took my voice recorder from my University days and attached it in the engine bay and started driving for 1 hour).. I had to basically listen to the whole one hour recording to get this one second sound !)...

Do tell me if you are able to listen to it or to download it...

thanks a lot for your help

[FROSTYBALLS]

Hello Michael - welcome to Toyota Owners Club

[Mikastef]

thx you. Hope this forum will be of great value to me as well as me to you :)

[CPN]

I have listened to it over and over about a dozen times and you're right, it is VERY quiet! Best I can come up with is injector "chirping" or something similar...

[Mikastef]

thx for replying my post :) !

I am trying to record it better this week. I am sure of the sound and It just came today again for 5 second and it was quite loud. I was basically at the stop line, and accelerated a bit much. The car made this loud strange sound on acceleration and stopped when I lifted my foot off the accelerator. When I re-pressed it, I didn't hear it again....

[Mikastef]

So guys , I went to Bosch CAR SERVICE today. Couldn't go Toyota since it is closed on Saturday.

So they put my car (and me) on an elevator around 2meter high and told me to accelerate.after 10 min of acceleration and inspection, they said that apparently all my other bearing (water pump etc ) seems ok. It also seemed to have no leaks around the exhaust connections (from engine to
back of the car).

They did a 'sight' inspection mostly but was quite thorough. They looked underneath the car's engine bay. And I also got the opportunity to swap place with one of the mechanic to look underneath it.

Apparently they think they heard something around the place where the gearbox meets the engine (I didn't - but my ears aren't that well trained). They said that perhaps a bearing near this connection is going
bad and I need to go to the agency...(isn't the automatic gearbox made up of lots of bearing??!)...they said that it does not seem to be the gearbox itself but the connection between the gearbox and the engine.
Apart from this possible problem, the car seems fine. When I was on the elevator, I didn't hear the car made its usual strange sound, perhaps because the car wasn't really on 'load' as it was accelerating in the
air effortlessly.

..I pray that their diagnostic are wrong !...I don't have gear slipping or something..my gearbox seems fine when I accelerate. I only get this strange sound...

plus I don't hear this sound when I'm cruising or I'm at high speed..only when I'm driving less than 60 km/hr and under load (perhaps it can be resumed to: when I'm driving at a slightly high rpm, under load and accelerating,with low gear and at a low speed).

I am trying to record it better since I do get this sound longer than my previous recording and a little bit louder sometimes...

I came across an article relating to spark knock which may originate from lots of other causes...I am currently investigating this path and I hope to Find a solution soon.

(Note : else I plan to leave my car at Toyota agency in two weeks if there is no solution. I depend 100% on the car due to my erratic work requirement and long commute time- that's why I cannot easily leave the
car at the agency anytime). Btw, at the mechanic place, we also put the car in neutral and accelerate a lot. No sound was heard.

[MikeSh]

I think this is probably a long shot but it just might be a loose spark plug.

Recently (on a forum for a different car) a guy had a persistent ticking/tapping which was ascribed to an injector. Then one day he got on the throttle and a plug blew out having stripped the outer several turns of thread in the ally head.

So might be worth checking they are all tight.

[Mikastef]

thanks mikesh for helping out. but i am sure it is not a loose spark plug. I did change my spark plug recently and the sound is always here.

I have attached some new recordings in which you can hear the sound Much better than before !.. you will definitely hear something
strange now ! Don't tell me it is nothing :)! I have compiled these recordings over several weeks of investigation.


LINK:https://www.dropbox.com/sh/n04pib5mastixcq/AABV6ppJcICPRuW3EV86o0Zba?dl=0


Note: the sound is NOT big at all - only 400 kilobytes total (so less
than 1 megabyte). therefore you can safety download all four.

Thank you for listening to it and trying to help out !

[Dan12345678]

I have this exact issue! Did you ever find out what it was?

[Dan12345678]

Praying it's not an expensive repair

[Bjon]

Any update On this? 

[donkeychomp]

An older post but I was going to suggest getting the front wheels off the ground on axle stands and feel for any play in them. Could be a wheel bearing starting to go.

[mrfixer]

A light metallic rattle under load suggests detonation/pre-ignition to me, or possibly a loose exhaust heatshield.

[flash22]

The op hasn't been on here since Oct 2016  and this was posted in May 2015