Sienna exhaust odor


#1

Have a '05 Sienna with almost 50,000 miles. Has been absolutly trouble free, 20 plus mpg. Never had any exhaust odor before this week, now has a strong “rotten egg” sulphur odor. What would be the most obvious thing to look at. Thanks, Marty


#2

Wait a week. Do nothing rash. This problem is commonly caused by a tankful of bad gas, specifically gasoline with a slight excess of sulfur. The odor may go away by itself after your next fillup.

If not, your Sienna may be running rich for some reason. In that case you would start by having the computer scanned for any troublecodes.


#3

That rotten egg smell are suphur compounds coming from the catalytic converter. In the 70s when these were introduced, GM and other cars had a warning about the smell, and it told owners not to worry.

That is still basically true, but since you did not have that smell before, you may have a problem with improper combustion in the engine or the converter is in need of replacement.

I believe new cars now have a longer emissions warranty, so you may be eliglbe for a free fix, if it is the converter.

If the engine has never been serviced, it could need new spark plugs. In any case, the engine should be tested to see if it meets emission, and the plugs are working properly. If all is OK with the engine, the converter would be at fault.

The only other cause I can think of is extrenmley poor quality gasoline, but I have only experienced that in third world countries.


#4

Actually, Doc, there was a class action lawsuit against Shell and (I think) Exxon in 2004 for excessive sulpher in gasoline sold in Florida and Louisiana. It was so poor that sulpheric acid was eating the electrical contacts in the gas pump assemblies. A quick search will turn up tons of info.

High sulpher levels in gas are not unheard of or even uncommon. In the early '70s when manufacturers were struggling with the implementation of cat converters and gasoline was whatever the refineries trucked in that rotten egg smell was a common problem. I don’t know the chemistry involved or what the “fix” was and whether it happened at the car manufacturers or the refineries, but the problem was eventually solved…mostly. Except for that car I was behind a few weeks ago…


#5

Thanks Mountainbike for the update. I knew in the 70s gasoline quality was spotty to say the least, but I assumed by 2008 these problems had been resolved in North America.

When I’m overseas, nothing surprises me, since in mmany countries people don’t complain or the standards cannot be adhered to due to faulty refinery equipment.