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rotten egg smell in exhaust=bad o2 sensor?

Discussion in 'General Explorations!!' started by tac0meat, August 12, 2003.

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    1. tac0meat

      tac0meat Elite Explorer<br><img src="/forums/images/stars4.

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      ok ive done a search and havent found much except somebody said if the exhaust smells like sulfur it is the o2 sensor. mine smells a bit like rotten eggs or sulfur so do i need to replace the o2 sensors? and how often should they be replaced? ive had the truck for 75k miles and have never replaced them(i dont think my dad changed them out in its preious 270k miles before i got it either)
       
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    3. Alec

      Alec Elite Moderator Moderator Emeritus

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      Or it could be the cat.

      If it's just rich (too much fuel) then it could also be your fuel pressure regulator.
       
    4. aldive

      aldive Elite In Memoriam

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      I too would suspect the cat.
       
    5. tac0meat

      tac0meat Elite Explorer<br><img src="/forums/images/stars4.

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      i just had one of the cats replaced a couple of months ago so i hope its not that, how can i tell if the fuel pressure regualtor is bad and how hard is it to replace?
       
    6. Glacier991

      Glacier991 EF Tranny Guru Moderator Emeritus

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      The following explanation is not mine, but out of my archives - on the WHY of the rotten egg smell:

      "The sulphur smell from the exhaust, is actually caused by running the engine/cat convertor slightly lean for long periods and then running under a rich condition (ie going up a hill under heavy load) This is when the sulphur smell (rotten egg) is produced.

      Under relatively lean conditions, the sulphur found in gasoline is converted to sulphur trioxide, then during the rich running condition the sulfur trioxide is converted into hydrogen sulphide (rotten egg smell) within the catalytic converter."

      So, you can try different brands of gas, or check and see if your Forward O2 sensor is lazy. If you are not getting a MIL (CEL) light, it's probably only lazy (e.g not switching fast enough.) Maybe you can find a shop with a O2 sensor tester. Before OBDII, that was the easiest way to see what they were doing. There is one for sale on the used and for sale section here. I'm guessing gas and maybe the lazy front O2 sensor.


      Happy, and less smelly, Exploring

      Chris

      ps. Western produced US gasoline and oil is high in sulphur. Quaker State ages ago used to ballyhoo their low sulphur content - being "eastern".
       
    7. padeerslayer03

      padeerslayer03 Active Member

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      my fuel pressure reg went bad a couple months ago but i had no bad smell except for fuel i could smell while driving. Also, it would be sluggish when accelerating, shifting, and going up hills. Black puffs of smoke came out the exhaust.
      Then went to start it one day and no go.
      for me, thats bad fuel pressure regulator.
      wasnt very hard to replace.
       
    8. Glacier991

      Glacier991 EF Tranny Guru Moderator Emeritus

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      And you never went lean. Therein lies the difference. Thanks for the post, it adds to the diagnosis. If your fuel pressure reg didn't cause rotten egg for you, probably isn't for him. Good addition.


      Happy Exploring

      Chris
       
    9. tac0meat

      tac0meat Elite Explorer<br><img src="/forums/images/stars4.

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      im gonna check into the o2 sensor, i only run chevron gas, and i dont think the o2 sensors have ever been replaced. how often should i have the o2 sensors replaced? mine prolly have 345k miles if theyve never been replaced
       
    10. Glacier991

      Glacier991 EF Tranny Guru Moderator Emeritus

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      Varies ... a lot. I've seen 50K, I've seen over 200K. I'm betting yours is working but getting lazy. Change the upstream sensor and let us know if it cures your problem!


      Happy Exploring

      Chris

      ps. Mine went 200K but was getting sluggish, so I replaced it.
       
    11. udmsvt

      udmsvt Well-Known Member

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      i got the egg smell in my old contour and had a clogged cat, removed the cat alltogether and still had some smell....at that time, i used all diff brands of gas.

      i had in in the ex for about the first 2 weeks (on citgo). i have run shell/texaco gas ever since and have never had it again. monil is good gas too, but never EVER use speedway!
       

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