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Fair enough on possible source of chemical smell, but I do not have the A/C running at that time. I can check to see if the pressure is good. I suspect it is fine as the A/C is ICE COLD, and no hose freezing is observed, common occurrence for low gas levels.

Thanks for something to review. :cheers:
Ammonia is not used in vehicle air conditioning systems, only in commercial refrigeration/freezing systems. Cars use - or used to use - freon, but now some sort of ozone-friendly halocarbon or something like that (sorry, I'm just a microbiologist, I can only talk about pathogens and how they kill you).

For our on-board chemist, have you figured out yet the reactions within the cat that would create NH3? And what - if anything - drives the reaction and what can be done to minimize?
 

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Your smell is Definitely Not coming from your AC system that I am sure of ...
I am not a expert but Ammonia can be a product of your exhaust , if your cat converter is very hot and you are not hard on the throttle ammonia can be present more so if your fuel mixture is running rich ... You may want to check, clean or replace your air filter and clean your sensor in the intake tube , as theses could effective your fuel mix to the rich side.
 

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Ok I have found the likely scientific cause of the ammonia smell. I also will provide the chemistry behind it.

Short Answer:
Toyota uses a Three Way Catalytic (TWC) converter. This style (not a toyota problem) has created a new problem for emissions that was unexpected for the previous Two Way Cat Converter. These Cats combined with the improved low sulfur gasoline in certain conditions have been shown to produce Ammonia from atmospheric NO, NO2,NO3 (Herein listed as NOx) entering the Cat Converter.

So certain fuel blends and/or combined with rich running fuel mixtures can shift the equilibrium balance to producing NH3. If the sulfur levels were the same as previous fuels, and air ratios correct then this should not occur to the level I am experiencing.


Stand by for proof
:cheers:

Whats most interesting to me is Ammonia is the major cause of atmospheric smog haze. So the unintended side effect through EPA emissions control is to have more smog. They are already designing a SWC Cat to address this . The TWC is just too good at reduction chemistry and conversion is not limited to HC and CO.


IF YOU SMELL AMMONIA YOU ARE NOT CRAZY!! :simmadown:
 

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Here is one scientific paper abstract addressing the issue, you can search the title on the internet.
Title

"Effect of low-sulfur fuels upon NH3 and N2O emission during operation of commercial three-way catalytic converters"


Authors:
Isidro Mejía-Centeno, Angel Martínez-Hernández, Gustavo A. Fuentes

Abstract
The use of low-sulfur fuel is known to improve the performance of the three-way catalytic converter (TWC). However, in this work we report how low-sulfur operation of commercial TWC also favors formation of N2O and NH3 as by products. We found that low-sulfur rich operation above 300 °C increases the production of NH3, inhibiting the formation of N2O characteristic of high-sulfur operation. During lean operation, the production of N2O near the stoichiometric point is not significantly affected by the sulfur level. The large production of N2O observed during light-off is not affected by SO2 when the operation is lean, but under rich conditions N2O is produced up to 575 °C. The increased production of NH3 and N2O in TWC as a result of the introduction of low-sulfur gasoline is an area that requires further analysis because of its implication upon public health in large urban settings.

Publication
Topics in Catalysis May 2007, Volume 42-43, Issue 1-4, pp 381-385

This paper reports a 100 fold increase in NH3 emissions in recent years that pose a health risk for the population.
 

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Table 1 shows normal reactions in a TWC Cat. Table 2 shows the side reactions when the system has very low sulfur and incorrect fuel ratios (here rich). Side reactions 9 - 12 occur with the right conditions (rich fuel, low sulfur) creating 100 fold increase in NH3.

https://lh5.googleusercontent.com/-mKH9_IdD0PQ/Um6A6UWVGvI/AAAAAAAAAW4/jfBeLDR7vxQ/s856/NH3%2520Tables.JPG?gl=GB



I have highlighted the NH3 production listed in referenced publication, showing increased NH3 production at rich fuel ratios.

https://lh4.googleusercontent.com/-VrP-T6zK3mE/Um6BH_meHnI/AAAAAAAAAXM/5onrRPOOpSQ/s589/Chart%2520NH3.jpg?gl=GB



So I think by cleaning my MAF, checking O2 sensor, and changing spark plugs I should be on the path to lower the NH3 emissions, but never truly eliminate them. When I do this I will let you all know if this has worked.

The next generation of Cat converters will be the better solution, but that not gonna happen at the moment.


HOPE THIS HELPS OTHERS:cheers::cheers::cheers::blueblob::blueblob::blueblob:
 

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Additionally for the H2S crowd, this will get produced with high sulfur gasoline and a fowled Cat converter.
Talk about backing up your claim. Wow. This is fantastic.

I hesitated to comment because I lacked any proof for my theory, but I was thinking...."if it smells like ammonia, it is probably ammonia."
 

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Talk about backing up your claim. Wow. This is fantastic.

I hesitated to comment because I lacked any proof for my theory, but I was thinking...."if it smells like ammonia, it is probably ammonia."
Thanks! It helped for the good suggestions on the topic. :clap:
 

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Ammonia is not used in vehicle air conditioning systems, only in commercial refrigeration/freezing systems. Cars use - or used to use - freon, but now some sort of ozone-friendly halocarbon or something like that (sorry, I'm just a microbiologist, I can only talk about pathogens and how they kill you).

For our on-board chemist, have you figured out yet the reactions within the cat that would create NH3? And what - if anything - drives the reaction and what can be done to minimize?
I didn't think so. It was worth a shot! I'm no expert! :smile:

Also, I did a little research based off of what our resident chemist said because I was curious and I saw this article. There is a section called "Unwanted Reactions," Under "Types."
http://en.wikipedia.org/wiki/Catalytic_converter#Types

It just corroborates what the chemist said, basically that catalytic converters can produce Hydrogen Sulfide and Ammonia.

Interesting stuff!

Ignore all grammatical errors or misspellings, because I sent this from my phone.
 

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Hi all - I know this is an old thread but I am now experiencing this in my '04 Toyota Sequoia. I've been doing lots of research and this, with all the chemistry info, seems to be the best thread I've found. What I'm wondering is, if changing my cat is going to fix the ammonia smell or was there something else in here I missed? All of the diagrams and big words got me a little confused. LOL

THANKS IN ADVANCE!
 

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No, the production of ammonia is a "side reaction" taking place during the normal operation of current generation catalytic converters. NH3 production appears to be enhanced by the use of low-sulfur fuel (which you have no direct control over), and by rich fuel-air mixtures, which can be triggered by a multitude of problems with an engine's fuel-feedback mixture control system.

So, the following can be contributors to rich operation:
1. Dirty mass airflow sensor;
2. Dirty/inaccurate intake air temperature sensor;
3. Inaccurate coolant temperature sensor;
4. Defective coolant thermostat;
5. Leaky fuel injectors;
6. Inaccurate fuel/air sensor;
7. Inaccurate oxygen sensor;
8. Vacuum leak;
9. Exhaust system leak;
etc., etc.

You can get a better idea of what is going on by connecting a monitor to the OBD-II diagnostic port and determnining what the engine's ECU thinks it is seeing as far as fuel-air ratio, and look at the long-term and short-term fuel trim values.
 
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