High nox fail smog test any remedies? 99

Over a decade late in this one, though the EGR system's purpose is to reduce the overall combustion chamber volume of the engine by means of reducing the combustible oxygen concentration in each cylinder by flowing inert uncombustible exhaust fumes into the cylinders. Nitrogen Oxide (NOx) is formed when the internal engine temperatures become 2,500 degrees F or higher.

The EGR system causes a reduction of internal engine temperatures since the ECU is allowed to inject a lesser amount of fuel since there is a lesser amount oxygen content. With less fuel being injected and less oxygen being compressed there is less heat produced overall.

Let's say a 2 liter bottle is a one cylinder engine. So we have an engine with 2 liters of combustible air. And it takes 100cc of gasoline to be compressed with the 2 liters of combustible air to have perfect combustion. This would be the engine without the EGR system activated.

Now with the EGR system activated it has flowed 1 liter worth of inert uncombustible gas, let's say nitrogen. The nitrogen has displaced 1 liter of combustible air, so now we only have an engine with 1 Iiter of combustible air; therefore it now only takes 50cc of gasoline to have perfect combustion.

When an EGR system is working as it should it will not only cause NOx to be reduced, it will also increase fuel economy.

Overall with an increase of NOx one would definitely want to check the EGR system if the vehicle is equipped with one. Primarily if the EGR valve is opening as it should and if there is a proper flow through the EGR air passageways.

Also ensure the cooling system is operating as it should. If the cooling system is not operating optimally and the engine is slightly overheating it will cause an increase in NOx as well.

If you also have the means of checking the inside of the cylinders for carbon build up this would be a good to inspect as well. Carbon will create hot spots and pre-ignition which will increase the internal combustion chamber temperatures, though typically you'll see an increase of HC and CO when this is a contributing factor to the NOx failure. If carbon build up is an issue, there are many products on the market that can help with this issue, though be forewarned that sometimes the engines sealing surfaces like the carbon being present if the carbon has been there for a long long period of time (the carbon may have worn into the metal sealing surfaces).

Anyway, if your vehicle has only failed on NOx and all other emission gases are relatively low. It would be recommended to inspect anything that could increase internal combustion chamber temperatures.

One little trick of the trade for reducing NOx if your HC measurements are low is to retard the timing a few degrees (retarding timing will often times increase HC). There should be a range of acceptable retard and advance degrees that are acceptable for you to still pass smog; you can always advance the timing after the smog test is performed if you'd like. ?? Over a decade late in this one, though the EGR system's purpose is to reduce the overall combustion chamber volume of the engine by means of reducing the combustible oxygen concentration in each cylinder by flowing inert uncombustible exhaust fumes into the cylinders. Nitrogen Oxide (NOx) is formed when the internal engine temperatures become 2,500 degrees F or higher. The EGR system causes a reduction of internal engine temperatures since the ECU is allowed to inject a lesser amount of fuel since there is a lesser amount oxygen content. With less fuel being injected and less oxygen being compressed there is less heat produced overall. Let's say a 2 liter bottle is a one cylinder engine. So we have an engine with 2 liters of combustible air. And it takes 100cc of gasoline to be compressed with the 2 liters of combustible air to have perfect combustion. This would be the engine without the EGR system activated. Now with the EGR system activated it has flowed 1 liter worth of inert uncombustible gas, let's say nitrogen. The nitrogen has displaced 1 liter of combustible air, so now we only have an engine with 1 Iiter of combustible air; therefore it now only takes 50cc of gasoline to have perfect combustion. When an EGR system is working as it should it will not only cause NOx to be reduced, it will also increase fuel economy. Overall with an increase of NOx one would definitely want to check the EGR system if the vehicle is equipped with one. Primarily if the EGR valve is opening as it should and if there is a proper flow through the EGR air passageways. Also ensure the cooling system is operating as it should. If the cooling system is not operating optimally and the engine is slightly overheating it will cause an increase in NOx as well. If you also have the means of checking the inside of the cylinders for carbon build up this would be a good to inspect as well. Carbon will create hot spots and pre-ignition which will increase the internal combustion chamber temperatures, though typically you'll see an increase of HC and CO when this is a contributing factor to the NOx failure. If carbon build up is an issue, there are many products on the market that can help with this issue, though be forewarned that sometimes the engines sealing surfaces like the carbon being present if the carbon has been there for a long long period of time (the carbon may have worn into the metal sealing surfaces). Anyway, if your vehicle has only failed on NOx and all other emission gases are relatively low. It would be recommended to inspect anything that could increase internal combustion chamber temperatures. One little trick of the trade for reducing NOx if your HC measurements are low is to retard the timing a few degrees (retarding timing will often times increase HC). There should be a range of acceptable retard and advance degrees that are acceptable for you to still pass smog; you can always advance the timing after the smog test is performed if you'd like. ??