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Ammonia smell from exhaust.

I drive a 2007 Toyota 4Runner. Recently the weather has been nice enough to drive with the windows open. I've noticed a very strong ammonia smell from the exhaust - so strong at times, that I have to roll up the windows and use the a/c. I use Shell gas with no ethanol, but it has a nitrogen additive. Is it the gas I'm using, or is there something wrong with the vehicle? It's definitely ammonia, and I can only smell it while I'm driving.


  • It wouldn't hurt to try a different brand of gasoline. Contact your Toyota dealer there might be a TSB for this problem.
  • A minute with Google does wonders. There may be a TSB.
    Check with your dealer.

  • "It's definitely ammonia..."

    It's definitely not ammonia. It's hydrogen sulfide -- big difference, and the Toyota folks are already aware of the problem. There is a TSB.

  • Hydrogen Sulfide and ammonia do not smell alike at all.
    If the OP is actually smelling Hydrogen Sulfide and confusing it with ammonia, it might be time to have a physical exam performed by an MD who specializes in Ear, Nose, and Throat. This could be indicative of a sinus problem as much as it is an automotive problem.
  • Being a chemist, I am very familiar with the smell of both ammonia and hydrogen sulfide, nothing alike. Thanks for the input everyone.
  • edited April 2012
    @Silverfin--I'm not much of a chemist. When I took a chemistry course, the only elements were earth, air, fire and water. However, isn't nitric oxide one of the byproducts of combustion and isn't it possible that this could chemically change to NH3? If Shell has a nitrogen additive, might this not increase the presence of nitric oxide?
    As I said, my knowledge of chemistry is pretty rusty, but you are a chemist so you would know if this is possible. I have a 2003 Toyota 4Runner V-6 which is probably the same engine that is in your 2007. I haven't noticed an ammonia smell, but I rarely use Shell gasoline.
  • edited April 2012
    I'm a little worried about a vehicle whose exhaust you can smell while driving the car. If you're driving around with the windows down you shouldn't be smelling exhaust. Maybe a little whiff once in a while if you're sitting at idle and the wind blows the right way. But if you're getting overpowered by exhaust to the point of putting the windows up you should worry about that first.
  • Ammonia can be produced by a catalytic converter. This is a dated (2007) but interesting article.
  • I took mine into Toyota last year and they showed me in the manual where some smell is described. I said that it was a very strong smell, we went on a test drive and said, "It was normal." Go figure????
  • Sometimes critters will crawl into a warm engine compartment for an overnight rest, and critters are also known to excrete a certain yellow liquid with an ammonia smell. If you got some critter liquid on an exhaust manifold or pipe or catalytic converter, when it heats up, you're going to smell it. Unlikely, but not impossible...
This discussion has been closed.