Exhaust smells like sulfur

Mazatrol · Dec 9, 2003

I'm posting this question on behalf of my son. He drives a 97 Toyota 4-Runner,V-6,2 wheel drive, with over 100K miles. He has kept the car well maintained with oil changes, tune-ups, etc. done per owners manual intervals.
Over the last year he has noticed a "sulfur" smell from his exhaust. It began slowly, but has steadily gotten worse. We have tried suggestions from many sources, but the problem still exists. So far he has tried the following: Ran a higher grade gas (premium) for several weeks...used fuel injector treatments in the gas...changed spark plugs and wires...and had the timing belt replaced. None of the above have given any noticeable change. When he first told me of the problem I suspected the catalytic converter, but several mechanics and exhaust shops have told me the cat probably isn't the problem.
All thoughts and advice are much appreciated.

deepsquat · Dec 9, 2003

I have always heard that was the catalatic converter also.

cangreylegend · Dec 9, 2003

Try using a different brand of gas and see if it helps.

JTK · Dec 9, 2003

I'd say it's most likely the sulpher content in the gasoline as well. Being that the truck is OBDII compliant (all 1996+ US vehicles), your "check engine light" would illuminate if the cat was bad. OBDII adds an oxygen sensor downstream of the catalytic converter that basically monitors if the cat is working or not.
G/luck
Joel

c502cid · Dec 9, 2003

I'm really surprised a mechanic hasn't figured this one out. Typically on a computer controlled car with a catalytic converter, a sulfer smell is an indication of a rich fuel mixture. The map sensor (if you have one) is telling the computer that the vehicle is under a heavy load and it is dumping in extra fuel. Have you noticed a decrease in mileage? If it was a GM vehicle I'd replace the map sensor and probably the O2 sensor too.

If you are into guessing, start with the O2 sensor(s) and see if you have a map sensor too.

Type of Gas has nothing to do with this.

Mazatrol · Dec 10, 2003

Many thanks to all for the great replies. I'm beginning to think that c502cid may be onto something. My son hasn't said if there is any gas mileage drop off. He HAS commented that the engine idles smooth in park but a little rough while in gear. This sounds to me like the engine is loading up (rich fuel mixture). He has not had a check engine light come on so maybe the cat is OK. I will copy and send this discussion to him and suggest that he start looking at the 02 and or map sensors next.
Thanks again for all the help.....great forum you have here...I plan to visit more often.

acranox · Dec 10, 2003

Well, my mother's old 88 Chevy S10 used to have a distinct sulphur smell. She mostly did city driving. Her mechanic told her to take it out on the highway every week and run it for 10 minutes or so over 50MPH.
She didn't really follow his advice, because it wasn't a real problem, but the smell did lesson for a few days after it had some time on the highway.
Just a thought.

theguru · Dec 10, 2003

I have had a similar problem in one of my cars. The car is fairly new, which may contribute, but it appears that it is caused by rich mixture (also maybe putting the foot down)loading up the Cat. I long drive may clear/ dry out the exhaust/ cat. The dealer has put it on their computer system and say it is within normal parameters. Car has only done 3,000km, which I have heard it is normal to run a bit rich when newish. It is a turbo and these do tend to run rich as well.

On the O2 sensor side, I had another car dyno tested this week and the tuner suggested that that their could be an O2 problem but not the O2 sensor itself but the earth at the ECU end.

Mazatrol · Dec 10, 2003

Thanks arcanox and guru for the replies. This kid travels constantly (state to state) so I'm sure the system stays cleared out pretty well. With all the traveling he gets a variety of gas brands and has been using a higher octane gas lately as well. I have just E-mailed him suggesting changing the map and O2 sensors to start with. I will post a follow-up as to the results.
Thanks again.

JTK · Dec 10, 2003

Like c502cid suggested, it could be a weak/failing O2 sensor causing overly rich conditions. With mileage over 100K those O2 sensors are likely very tired. Often they'll work just good enough as to not throw an OBDII code & set off the CEL, but MPG's, performance & emissons will suffer slightly. At that mileage I'd replace just the pre cat oxygen sensor(s) anyway. Hopefully it's a single cat system! As far as stinky (sulphur) exhaust being inherent in certain vehicles, I believe this to be true. We have 3 isuzu vehicles in the family (2 rodoes, 1 trooper- all 2002+) These trucks stink badly on certain brands of gasoline, and dont on others. They are fairly powerful, gas guzzling, heavy breathing beasts though

.
G/luck
Joel

DEWFPO · Dec 10, 2003

My experience has been that when you start getting that sulhur smell from your exhaust, your vehicle is running too rich. I tried a test and made my truck idle rich and sure enough it stunk like heck, leaned it back out and the smell went away. My cat was working just fine.

You might have a bad o2 sensor.

DEWFPO

[ December 11, 2003, 01:22 AM: Message edited by: DEWFPO ]

theguru · Dec 10, 2003

quote:

Originally posted by Mazatrol:
With all the traveling he gets a variety of gas brands and has been using a higher octane gas lately as well.

I believe the higher Octane fuels also have other additives not just higher Octane. I think most of the gas companies used to add cleaners etc to all their fuels, but now only to the higher priced Premium fuels.

Shell Optimax here (98 RON) seems to have a fairly high suphur content and does give my car that suphur smell, more so than some of the newer high octane fuels.

jsharp · Dec 10, 2003

Mazatrol -There has been a lot of discussion on the Toyota boards about this although the '03 models seem to be the most mentioned.

You might try here - http://www.4x4wire.com/forums/categories.php?Cat=

and here - http://www.yotatech.com/index.php?s=

and do a search. I haven't followed it but I'm not too sure there wasn't a TSB on this...

Virtuoso · Aug 24, 2004

Running rich and a high sulpher content in fuel can both cause it.

http://www.autoshop101.com/forms/h64.pdf

friendly_jacek · Aug 25, 2004

quote:

Originally posted by jsharp:
There has been a lot of discussion on the Toyota boards about this although the '03 models seem to be the most mentioned.

True, I have 2003 corolla with the problem. 04 is affected too. It is not just smell but smell/poor MPG combo.
So, I think there is a link between running rich and smell.

Update: Toyota admitted wrongdoing and produced new TSB, reversing its position and allowing to reprogram ECU AND replace cat with new design (this one with nickel, I bet).

friendly_jacek · Aug 25, 2004

thanks, nice resource on catalists.

Exhaust smells like sulfur

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