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Q: failed emissions for NOx on 1993 Toyota Corolla

My car failed for NOx and the limit was 1072.0 and it failed with 1467.1 so you can see it didnt fail for much any suggestions on what could be the problem and fix.. thx alot
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Most NOx failures are due to faulty egr systems. It would be a good idea to have your egr system thoroughly inspected and repaired as necessary. Also, don't forget to double check the ignition timing - if the timing is off that can affect NOx also. If the egr system and timing are OK then the problem becomes more difficult. NOx gases are formed due to excess heat in the combustion chamber. Carbon build up in the cylinders and cooling system issues are just two examples of item which can cause high NOx readings.
Any big chain auto parts store chain will scan it free. In Southwest Florida, Advance Auto parts, Autozone Auto parts.
Thx alot guys i am going to look into that but does it matter that my check engine light is NOT on?
I am not quite sure what the trouble codes are i just know the engine light is not on but it wont pass because of NOx if there are codes please tell me and i will figure out how to get them. I am not that smart when it comes to cars so you have to be really specific thx alot really apprieciate this thx
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