I will admit, I am new to the 4th gen runner. Just bought mine 2 months ago.
But, and I don't know the specifics of each truck, in general the "sulfur" smell will decrease as the cat system ages.
To give you an idea, here is this, from a Miata TSB. Similar smell, and they all but admitted it is normal and to deal with it.
http://www.miata.net/garage/tsb/01-043-06-1678.pdf
Again. I am new to the 4th gen, but I do know cars and in general the next few things are true about modern catalytic converter systems on modern (american, Canadian and EU) vehicle systems.
1. Sulfur is a normal smell during Cat operation. The degree to which this happens is dependent on MANY variables. The different percentages of the rare minerals in the cat that create the reaction to reduce harmful emissions. The amount of sulfur in the fuel. The load on the engine (heavy loads "overwhelm the system".. etc. etc.
Everyone on here knows this. No one is arguing it means the cat is malfunctioning. We are upset at the degree to which it smells. I totally understand.
Obviously I am doing some research on my own, but in general, as the cat ages eventually the sulfur smell decreases. This is due to the "aging" of the cat itself.
So, I guess what I am saying is, I am not sure putting a NEW cat is the solution. I keep seeing people running to get a new cat, when that is probably the EXACT opposite of what you want to do.
Unless you want to cut it off, please don't for the sake of everyone healthy air, then we may well have to suck it up and let the cat's age. FYI, I have a 2005 4runner with the original Cats and have 110k miles and I have almost no horrid smell. Only if I floor it, with my window down, do I get it. I take it as meaning it is working and go about my business.
I looked at Toyota's TSB for it and I think it may well be just to appease people, similar to the gas pedal recall. We have no shown that it was driver error, not some problem that lead to the accelerations; but we still get the pedals shaved to help with the urban myth factor.
My .02 cents.
From an expert:
"It's (the smell) hydrogen sulfide or H2S. It does not exist in the fuel or oil, which is why you can't smell it at the gas station. It does, however, come from the gasoline. Almost all gasoline contains organic sulfur compounds with sulfur levels ranging from 30 to 100 parts per million, approximately.
"As the fuel burns, the organic sulfur compounds break down into simpler compounds. If the engine is running lean (more air than is needed to burn the fuel), the sulfur is likely to be SO2, or sulfur dioxide. The catalytic converter can change this into SO3 (sulfur trioxide), which then reacts with the catalyst to form sulfates on the catalyst. Over several minutes there is a build up of sulfates. If the engine suddenly starts to run rich (not enough air to burn all the fuel), such as when you stop at a red light, climb a steep hill, or brake hard to slow down, the chemistry changes. Now the sulfates are unstable and they react to form hydrogen sulfide, which is expelled from the exhaust pipe all at once. The high concentration is the reason for the bad smell! This effect is a common problem with new vehicles because the catalyst is working at a very high efficiency. However, as the catalyst gets older, the activity drops. Fortunately for us, one of the first reactions to be affected is the formation of hydrogen sulfide. So as the catalyst gets older, the smell will go away. It should also be noted that many catalysts never smell bad. One reason might be because the vehicle doesn't run lean for much of the time, or perhaps the catalyst has an extra component that reduces the production of hydrogen sulfide.
"Next time Eggbert and Shelley stop behind a vehicle that smells bad, they can be grateful that it's at least not contributing much to atmospheric pollution."
Thanks to this month's Whizard, Dr. Gordon Bartley, a senior research scientist in the Emissions Research Department of the Automotive Products and Emissions Research Division. Bartley specializes in the development, aging, and evaluation of vehicle emission catalysts.
Read more:
How can you tell a catalytic converter is bad
