By on December 8, 2010

TTAC Commentator dastanley writes:

Well here I am again on Piston Slap about my 2006 Corolla w/ about 44k miles. This isn’t a burning question (no pun intended), I’m just curious. This time it’s the exhaust – it stinks. I know that the rotten egg smell comes from the catalytic converter, but why? Is the engine running rich and overloading the converter?

The check engine light isn’t on and the gas mileage is about the same, so the computer (apparently) hasn’t detected a problem. I use regular 86 octane fuel (high altitude), mostly Conoco-Phillips with “Pro-Clean”. I’ve been told that the fuel in this region of NM has a high sulfur content, although I can’t confirm that.

The exhaust odor doesn’t bother me when driving around (I’m not following my own car), but every time I pull into the garage, it smells pretty obnoxious and my wife thinks I’ve farted. WTF?

Sajeev Answers:

How the heck can you stay married when you do sulphur farts in front of your wife? It’s time to lay off the eggs and give up on the cabbage soup diet. Oh wait, you rang about the smell in the garage, not in the bedroom.

What’s happening to your Corolla is not rare. I’ve seen this many times during my 10-year quest to learn more about cars via message boards. The same two fail points always come up: Oxygen Sensors or catalytic convertors. In my experience, replacing the O2 sensors alone will clear up your farts. This is because they are gummed up with the same sulphur deposits in your catalytic convertors. But while the convertors can’t do much, the O2 sensor adjusts the air/fuel mixture, effectively toning down the amount of fuel/sulphur in your system.

Plus, replacing a catalytic convertor is a bit more than the $100-ish needed for a couple of sensors on a Corolla. New sensors, a healthy number of high throttle, high load runs down the highway (in 2nd and 3rd gear) and your problem should disappear like a ninja fart in a movie theater. If not, do one more thing before changing the cats: seafoam the motor for maximum diuretic bang for the buck.

And for the Seafoam newbies out there, keep this in mind: as with any good marriage, make sure you Seafoam your “system” away from those you care about.

Send your queries to [email protected] Spare no details and ask for a speedy resolution if you’re in a hurry.

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27 Comments on “Piston Slap: Sulphur Farts...”


  • avatar
    ash78

    Worse comes to worse, I’m assuming the Corolla has maybe one upstream and one downstream sensor. Replacement should be around $50 each, and you don’t generally have to do the downstream one–it’s passive and only reports on the condition of the cat. The upstream sensor usually sends lean/rich info to the ECU, so it’s an active part of fuel economy and exhaust contents.
     
    Remember, a CEL only shows up when a certain threshhold is exceeded–it doesn’t mean there’s no problem at all, only a problem too small to trigger the idiot light. Take action now to avoid trashing the cat. Another quick acid test would be to run a couple of tanks of a different brand and/or octane of fuel.

    (disclaimer: I don’t know Corollas specifically, I’m speaking generally about most modern fuel/exhaust systems from personal experience and lots of research)

  • avatar
    Contrarian

    If you always use the same gas station, try switching for a couple of tanks.

  • avatar
    grzydj

    If there is a problem with the catalytic converter, it is covered by federal law to be replaced up to 80k miles.
     
    http://www.epa.gov/oms/consumer/warr95fs.txt
     

    • 0 avatar
      psarhjinian

      I was going to say this, and it might not be a bad idea to get it looked at anyways while the emissions-control warranty is still in effect.

    • 0 avatar
      dastanley

      If there is a problem with the catalytic converter, it is covered by federal law to be replaced up to 80k miles.

      That’s certainly good to know.  New Mexico doesn’t do emissions testing (maybe the city of  ABQ does?), but if I were to move it might be an issue in another state.  Also I imagine if the converter died and slowly plugged up as I continued to drive, my performance and mileage would suffer and become increasingly obvious.  That’s good to know it’s covered for 80k miles.

    • 0 avatar
      Educator(of teachers)Dan

      Yeah, ABQ does testing has centers all over the place.  The rest of the state doesn’t give a rat’s ass.  I often fantasize about buying say a 1984 Pontiac Pariseanne and dropping a 5.3 ltr Vortec in it, computer, transmission, and all.  That sort of thing is illegal in California but in NM, who cares?  Plus it would likely be a cleaner engine than the stock iron excuse for one.

  • avatar
    dastanley

    Also, any suggestions on the best places to buy O2 sensors?  Perhaps Autozone or online?  I read an article on cleaning the O2 sensors and it suggested using a welding torch to burn off the carbon buildup, so in my case I’d best buy them. 

    • 0 avatar
      grzydj

      Amazon.com has a good selection and good prices. I like Rock Auto because you can also talk to somebody on the phone too.

    • 0 avatar
      ash78

      Your question is better answered as a general “where to buy good parts online”
       
      AutohausAZ has great prices/shipping/service for most makes and models. That’s my best generic advice for car parts, and it’ll arrive overnight since you’re one state away.
       
      Most cars have plug-n-play models and generic versions that might require some wire splicing. You’ll also need to borrow (free) an O2 sensor wrench from Autozone, Advance, etc. or buy one on ebay for ~$20.

    • 0 avatar
      dastanley

      Thanks ash78.  I appreciate your advice.  I’ll check out that website.

    • 0 avatar
      Wheeljack

      While I’m no stranger to aftermarket parts, I tend to be somewhat leery of aftermarket engine sensors and actuators thanks to several bad experiences. That said, I wouldn’t be surprised if the OEM O2 sensors were made by NGK (Bosch is the other 800lb gorilla in the O2 sensor world) and if you can find NGK sensors in the aftermarket, then they will probably be fine. I’m not sure if I’d trust the aftermarket for a TPS or an IAC motor though…

    • 0 avatar
      golden2husky

      Go to Rock Auto.  They have great prices and several brands to choose from.  They also have a 5% discount if you have the code.  To get it, go to Taurusclub.com and search “Rockauto discount code”.  Copy and paste the most recent one in the Rockauto checkout procedure where it says “how did you hear about us”…The Rock Rocks!!!

    • 0 avatar
      M 1

      I shudder to think about how much money I spend at RockAuto each year. I can even find parts for 50’s cars there — and all at really great prices that even reliable sources like NAPA usually can’t touch.

  • avatar
    Domestic Hearse

    Could be worse. Once had a Cadillac that smelled like dirty diapers.

    • 0 avatar
      Robert.Walter

      Had a buddy that spilled a gallon of milk in the back of his Acura TSX…

    • 0 avatar
      Domestic Hearse

      Robert,

      Only, I don’t have children. The Cadillac mustered up that stench all on its own. Assumed it was the catalytic converter.

      Not as bad as the Infiniti J30. Every time the HVAC was turned on, it emitted eau de manure. AC design flaw — held moisture, grew mold inside.

  • avatar
    chris724

    I don’t really have any advise on this issue, but I definitely have noticed the sulfur stink almost always comes from Toyotas. And it’s usually when they’re doing a WOT run, i.e. pulling out in front of me.

  • avatar
    Stingray

    I think he has to stop feeding beans to the… car?
     
    I haven’t seen that SeaFoam before, what it does?

    • 0 avatar
      potatobreath

      I believe Seafoam is a solvent that goes through the brake booster vacuum line to clear the intake manifold and combustion chamber of carbon deposits. It can also go into the engine oil before an oil change or in the fuel tank to clear the fuel system. I only use Seafoam for the vacuum line though; for fuel I prefer to use a bottle of Techron. Seafoam applied properly into vacuum line results in a really big smoke show. The entire can of Seafoam all at once in a vacuum line results in a hydrolocked motor.

    • 0 avatar
      potatobreath

      If making big Seafoam clouds seems antisocial, then there’s the Italian tune-up option: high RPM operation on a quiet stretch of (twisty to suit) road for a few minutes. :)

  • avatar
    Hank

    Every time I’ve ever smelled sulphur on the highway I’ve been behind a Toyota of one model or another, without exception.  It’s seems to be a prolific problem…enough so that I always try to avoid getting stuck behind Camrys…unless I’m trying to cover up something else.  “Oops, must’ve passed a Camry!”

  • avatar
    dastanley

    Ah yes, the Italian tuneup.  Ironic that living out in the desert, we use the Corolla more for stop and go city driving.  On occasion, we’ll do a road trip to ABQ, PHX, or DEN, but not usually in the Corolla.  I need to open it up on the Shiprock or Bisti Highways when the Navajo Nation police aren’t around.  They tend to stop white boys like me for speeding in their sovereign nation – wonder why?

  • avatar
    dastanley

    Thank you Sajeev for running my question and for the advice.  And thank you TTAC Best and Brightest for your advice and comments as well.  I appreciate it!

  • avatar
    afuller

    My wife got a recall notice in the mail for her Toyota Matrix regarding stinky exhaust.  Toyota replaced the converter and probably some other stuff; I can’t remember since this was last year. 

    It may be something to look into.

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