I hope someone can help me out. I've been having a sulfur smell coming from my car when I drive at higher speed (60+) for a few months now. If I have the windows cracked it is really noticeable. I have tried Sea Foam and always run 91 or higher gas. I just took it to the shop today to put on the computer and no codes showed up. Mechanic said everything was fine. I'm confused, something has to be going on. Any ideas would be great.

 

Time to replace the main cat under the car, sound like yours is all plugged up a sure sign is that wonderful sulfur smell

 

Thats what I was thinking. But its odd the computer didn't pick up a code and doesn't a clogged cat usually effect the cars performance?

 

yes performance should suffer, crappy gas mileage and poor power would be good indicators ... but you may not be totally plugged yet ... it would depend on what you were doing that brings on the sulfur smell if you had just been at wot the car would have that sulfur smell if there was some blockage

 

Yea it usually only smells after I get on it or just driving on highway at high speed. You say you think its the large one on bottom?

 

It is typically the main cat that throws off that wonderful smell, you could opt for a fast cat replacement

 

Cats make that smell because they're working too hard. (rotten eggs/sulfur)


This is usually caused by a cat that is 'full' of contaminants, and almost plugged, causing the exposed portion of the Catalist to work much harder to compensate for the plugged portions.

This does not always result in a code because the cat is still working, it's just working TOO hard.

The cause of your problem (bad cat) needs to be fixed. Usually this is caused by bad engine controls/management. This can range from a bad injector, or O2 sensor, to fouled spark plugs or a plugged air filter. There's a lot to check. Have a good mechanic monitor the O2 readings and fuel trim. Or check Nissan's standard 'Optimal' specs and check it yourself. This will help you pinpoint the issue.

Replacing the cat will likely fix the smell, but not the real problem.

Also, any shop can check which cat it is fairly quickly with a temp gauge, checking running exhaust temp before the cat, and after.
The bad cat in your case will show a MUCH higher temperature reading After the Cat.

-Matt

 

i see what you did there tuner

 

Thanks Tuner. Appreciate all the information. What would be the easiest way to go about checking it myself?

 

Every car I have driven one with only 15000 miles has had that smell only when you wot or very close to it. Are you telling me that a 1 year old car with 15k would have clogged cat. I would understand my max with 144k but not a car with 15k.

 

You need a temperature gauge, infared style is best. Local auto parts place may rent them, I don't know.

You want the car running at idle, check the temperature (point the infared gun, like a lazer sight) before the Cat, and after the cat. measure the readings. You can post if you're unsure. Check all three cats.

These numbers are random, the DIFFERENCE is what's important, difference in readings should show:

400*F before Cat, 475*F after the Cat. (anwhere from 20*-140* higher is normal)

Your bad Cat will probably read something like this:

400*F before Cat, 625*F after the Cat.

The higher the 'after' temperature, the harder the Catalitic Converter is working.

If you ever see the SAME temperature, or LESS after the cat, then that cat isn't working at all.



The other way is a pressure test, but that's more involved.

 

Thanks a lot tuner. I'm definitely gonna check that out this weekend.

 

No problem man. Just don`t forget, you`ve probably got another issue causing the cat to plug up quickly, and cat`s aren`t cheap, you don`t want to go replacing them often, so repair the problem that`s causing the bad cat.

Post the Temp readings if you`re unsure about them.