Ammonia smell? - Page 4 - Toyota FJ Cruiser Forum
Misc. Technical Discussion For all technical info that doesn't have a category

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post #31 of 32 (permalink) Old 05-09-2017, 11:02 AM
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Re: Ammonia smell?

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

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post #32 of 32 (permalink) Old 05-09-2017, 01:57 PM
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Re: Ammonia smell?

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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