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mike100 · 05-10-2013

NOx is very sensitive to ign timing, combustion temps (EGR help this), coolant temp, and fuel mixture. The air/fuel ratio at which NOx is minimized is a very narrow range and the oem calibration strives to keep it there during light loads and cruise conditions.

On mine, I found that changing out both of my 22 yr old O2 sensors did the trick and lowered the NOx significantly- like nearly half as much output.

05-10-2013	#4
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,786	Re: 1990 LT5 emissions fail NOx is very sensitive to ign timing, combustion temps (EGR help this), coolant temp, and fuel mixture. The air/fuel ratio at which NOx is minimized is a very narrow range and the oem calibration strives to keep it there during light loads and cruise conditions. On mine, I found that changing out both of my 22 yr old O2 sensors did the trick and lowered the NOx significantly- like nearly half as much output.