Cold start exhaust smell

[xpeteyjtx]

Hey,

On a cold start, I notice that there is a sweet exhaust smell (while standing next to the car). My parents' cars also have this similar smell once in a while. I am assuming that a cold catalytic converter is the cause of this... but does anyone have any more insight? Is this smell dependent on the type/condition/composition of fuel? I am willing to bet that most of you have noticed something similar.

I own an 07 Yaris with 28,000 miles. First few oil changes were dealer oil. I have been done the last 2 changes with Castrol GTX. Mostly highway miles. No visual loss of coolant and no noticeable oil loss.

 

[c3po]

Hey, I would check your exhaust pipes, take a look at your tailpipe and let us know what you see. It may or may not be:

1) oily
2) Wet with junk
3) Black meaning some carbon

Has this car ever overheated, it might not be a bad idea to check your PCV.

 

[hemitom]

normal condtion of cold convertor. DO NOTHING. also some fuels smell more than others.

 

[tom slick]

normal, your hunches are correct.

 

[mechtech2]

If the smell continues after the car is up to running temp, your cat is shot. If your cat is shot, find out why. A bad O2 sensor or other engine management or fuel system is most likely bad.

As it is, some cars stink when cold, some don't. It's not time yet to get parts for yours.

 

[xpeteyjtx]

Nope, the exhaust pipe is clean. Not running anywhere close to rich.

I know it's normal... I'm just wondering what it is... NO? hydrocarbons?

Maybe I will experiment with different fuels.

 

[c3po]

If his converter is shot, would this mean it is clogged, and he would notice a decrease in engine power.

 

[AcuraTech]

Probably just gas additives and some unburned fuel you're smelling. Try switching fuel brands to see if it has an effect.

 

[simple_gifts]

I have a sweet smell with my echo since day 1; now 170K miles, never a CEL. Might have to do with the 10% ethanol.

 

[PandaBear]

exhaust leak on the manifold or gasket before the cat.

 

[xpeteyjtx]

Originally Posted By: PandaBear
exhaust leak on the manifold or gasket before the cat.


But the smell eventually goes away.
Or does it go away because the car is not running as rich as time passes?

 

[moribundman]

Originally Posted By: xpeteyjtx
Hey,

On a cold start, I notice that there is a sweet exhaust smell (while standing next to the car).


A cold cat produces more of a rotten egg (sulfuric compounds) smell than a sweet smell. Sniff again...

 

[mechtech2]

The cat works when it is HOT.
When cold, it is simply passing the gas.
A smell then is almost expected.

I have a Hyundai V6 that runs very well, but stinks when cold. Most cars don't stink when cold, but some do.

 

[xpeteyjtx]

Originally Posted By: PandaBear
exhaust leak on the manifold or gasket before the cat.


I started it up today. It was cold and there was some of the usual smoke from the tail pipe. I checked under the car and also checked in the engine bay and could not locate a leak.

Originally Posted By: moribundman
A cold cat produces more of a rotten egg (sulfuric compounds) smell than a sweet smell. Sniff again...


It almost smelled like rotten eggs. Seems more sweet to me... it's sort of enjoyable

 

[moribundman]

Originally Posted By: xpeteyjtx
Originally Posted By: moribundman
A cold cat produces more of a rotten egg (sulfuric compounds) smell than a sweet smell. Sniff again...


It almost smelled like rotten eggs. Seems more sweet to me... it's sort of enjoyable


It's not really suitable as aroma therapy, you know.

My guess is you do smell the smelly cat. How's that song go again?

 

[Gary Allan]

Quote:
Might have to do with the 10% ethanol.


That's my thought. Never noticed it until the fuel got ethanol.

 

[Ohle_Manezzini]

Ethanol makes sweet esters in a chemical factory as an engine?

 

[AntsinmyEyes]

coolant being burned on startup has a sweet smell. if there's alot of it it will dump out white smoke too

 

[Hokiefyd]

Yeah, I'd describe just-started exhaust as "sweet smelling". Both of our vehicles have a slightly sweet smell when idling stone cold. The smell does go away as they warm up.

 

[SumpChump]

My Toyotas are sweet at startup. Aoromatic fuel sweetness.

I once had a 1979 Olds Delta 88 with the 350Rocket. It stunk like burnt hair on winter startup. Mighta been the yellow bottle of Heet that I had in it.

There is an old 1980's-early 90's Ford F250 Dually in my neighborhood that has a glorious warm starchy raw potato type of smell to it. It took me back in time first time it drove by.