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Rotten egg/burning smell when going uphill?


WazWii
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Does anyone get or know the following cause of the issue I am going to describe below?

Basically on my last drive out I noticed a rotten egg/burning smell coming into the car cabin when going up three hills on different parts of the journey. Hills were not steep; they were more long inclines so yes car was under more stress than driving straight but the revs never really exceed 3,500 RPM. 

Smell was not exceptionally strong but it was there. Suddenly as I would get to the top of the hill and go back down or level straight again the smell would suddenly and quickly disappear. No lingering. 

Weather on the day was extremely cold (about 1-3 degrees Celsius). 

Initially I was leaning to a catalytic convertor (CAT) issue. For instance the catalytic convertor becoming jammed/blocked/malfunctioning due to the increased load of engine. Also maybe faults with the fuel pressure/fuel oxygen sensor or fuel filter. Issue has been there (to a much lesser extent) when I first got the vehicle so very confused. 

Other causes could be oil leaks or transmission oil leaks. There could also be carbon compounds and sulphur in the CAT that have built up that are now being blown off. So hard to know what it is. 

I was told it could potentially be the clutch also. I was in gear when going uphill with little changes. But I have a MMT in my Toyota Aygo so maybe on hills the clutch is always being ridden? If so how can I avoid this and if so it has been doing this since I got the vehicle. 

I sure hope it is not the clutch due to the expense of replacement but then again if said smell was occurring on a virtually new clutch at the beginning of my ownership then the same will apply to a new clutch which is worrying. 

I am hoping also someone can let me know that whatever the smell is, what health hazards is it posing to me whilst I drive and what options I have to have some in-car diagnostics done to ensure whilst I drive that I am breathing in clean-air. Will my local dealership have any such tools to do such a diagnostic? 

Only other issue I can think of is that maybe I need to put some premium fuel into the vehicle and see if that makes a difference. I doubt it will but worth a try. I did my research and in general on the online forums you can see this is an issue Toyota cars have; particularly with their CAT'S.

Hope someone can chime in here. 

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It's Hydrogen Sulphide from the exhaust. It is normal for it to be more profound when under load.

It's the same gas that makes a frat smell, not methane as some people think. 

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Hi, 

it sounds to me like a slipping clutch more than anything else from the list. Usually when the friction plate is worn the clutch start to slip when the car is loaded, particularly going uphill greater torque is required and here is where the clutch probably has started to give away and create that unpleasant smell, usually should it smells like cutting metal or dentists. If the smell does not return again while driving on level roads very likely to be the clutch, plus if it’s from the cat the smell will be difficult or impossible to be noticed inside the cabin since will go out from behind of the car unless there is an exhaust leak somewhere on the front. 👍

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As it was under load It's likely to be the clutch, what is the mileage on the car, the clutch actuator can cause problems with the MMT by not releasing the clutch fully

does the car still creep from a stand still ? The clutch maybe worn and it just needs recalibrating

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On 11/23/2021 at 2:39 PM, TonyHSD said:

Hi, 

it sounds to me like a slipping clutch more than anything else from the list. Usually when the friction plate is worn the clutch start to slip when the car is loaded, particularly going uphill greater torque is required and here is where the clutch probably has started to give away and create that unpleasant smell, usually should it smells like cutting metal or dentists. If the smell does not return again while driving on level roads very likely to be the clutch, plus if it’s from the cat the smell will be difficult or impossible to be noticed inside the cabin since will go out from behind of the car unless there is an exhaust leak somewhere on the front. 👍

Hi, it does not smell anything like cutting metal or dentists. It is a rotten-egg smell. The CAT in the Aygo is at the front. I believe it is mounted to the engine.

On 11/23/2021 at 2:56 PM, flash22 said:

As it was under load It's likely to be the clutch, what is the mileage on the car, the clutch actuator can cause problems with the MMT by not releasing the clutch fully

does the car still creep from a stand still ? The clutch maybe worn and it just needs recalibrating

Hi, mileage is around 30,000. This is an issue that has been present for some time - it also happens when revs are increased to a high-range. For instance in E mode with the MMT I used to have an issue where the vehicle when going up steep hills downshifted automatically resulting in too low a gear. The revs would go crazy high - in E mode I would be stuck with this gear all the way up the hill resulting in a smell. I worked around this issue using the M mode of the transmission. There are a few threads about this on this forum. 

Thinking of it now on all three drives before this one I went on similar gradient hills (if not steeper) at similar speeds and the smell did not occur at all...

Outside temperature was warmer on all those days. 

The car does creep. However even here from the onset of buying the car there would be periodic dead zones where it would not creep. What the car (transmission/clutch/ECU) is figuring out within this time I do not know. But it only occurs rarely. 

What will the re-calibration do? Further will adjusting the clutch cable be able to solve this? Maybe set it so that less wear occurs on the clutch?

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Its a MMT so doesn't have a clutch cable, It uses a clutch actuator on the gearbox - if it has had the issue(s) for a while you could have burnt/glazed the clutch, I would get someone to look at it and look at the MMT data with a scan tool - it may well have a code(s) stored in the TCM

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  • 1 month later...

Mine does that too, going up hills or reverse smells awfull, like rotten eggs, then it goes away. I decided to ignore it and open the window. 

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Its the CAT you can smell.I occasionally get this smell too on the wifes Aygo auto.Its only done 2500 miles so i take it that its normal.It doesn,t slip in gear or anything.I think its just getting very hot giving off this smell.

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