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The truth behind the egg smell.

1086 Views 11 Replies 5 Participants Last post by  nac704
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ok a few mechanics have told me that the egg smell isnt always the cat like a bunch of people think but in fact due to running your car too lean. If you just popped on a new exhaust and intake thats probably why. Its probably not your cat. Just thought I would share that I just read a post where someone said they were gonna get a new cat to get rid of egg smell. save money on the cat and get a tune up. - Jayson
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I dont get this that often, but I can produce the smell sometimes if I hammer on it hard, for a while, then ease off and hammer some more. OCCASSIONALLY i get the egg smell,andits only at highway speeds.
I have had the egg smell occur when hard on the gas from the time my Cougar was new until this point regardless of mods. It used to be that when you bought a new car it would do that at the start when going up hills, because of pushing the engine a little harder, but mine never has gone away in 38k miles.
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In one of the recent Road & Track issues there is an article that explains how catalitic converters work. Really interested. And yes the rotten egg smell is caused by the car running lean. I would recomend that article it is very interesting. I will post the month of the issue later.
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My cougar only has about 14k miles on it and it has had the rotten egg smell all along. Usually when I am on the entrance ramp to the tollway/freeway. Yes, I like to put my foot in it a little! (who doesn't?) I have no performance mods (yet) and I get this smell almost every day! I figured a new exhaust would remedy the problem, but you guys still have the smell? I often wonder if it smells as bad to the people behind me as it does in my car
Let us know about that Road And Track issue, I would be interested in reading that.
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Haven't a few people changed there catalitic converters and eliminated the problem?
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another cause of the sulfur smell is the sulfur content in the gas you use. Some grades/brands of gas have more sulfur content in them than other brands/grades. After I got the car, before the borla, I would stomp on it, and get the smell, and the mechanic asked if I'd changed the exhaust, after I told him no, he said upgrade to mid grade gas. I did as was recommended and I haven't had the sulfur smell anymore.
i had that rotten egg smell and they replaced the cat converter and it went away right away


they suggested better gas and i did that didn't change a thing
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just like heather was saying... i never got the smell... one day i went to pump gas in my car and i ended up putting in mid-grade (instead of high grade) and i actually got the smell... i mentioned it to a few people i know and they litterally asked me if i changed to a lower grade gas, that's when the light bulb went off....
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I almost always use 93 octane or better. The rare times that I go cheap, it really makes a difference with the smell. I still have the stench even with good gas just not as bad or as often. I wonder what makes the difference. Maybe the gas in this area is just all bad! It's certainly expensive enough, I paid 1.89 last week and they raised the price again the next day by about 12 cents. I think I have the conspiracy figured out...charge more for the gas and put a bunch of additives in it too!
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I usually use the 87 octane gas. My exhaust doesnt smell ever.. I find that if i use mid or high grade i get more ugly black buildup on my exhaust tips than if i use the 87 octane stuff.
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Mine smelled when I used 89...so I said F it and am using 87 now. Why waste the xtra cash ??
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