You said that you passed the EGR but failed the NOX readings?
Yes. The EGR computer self test. I had to replace the VSV and did the checkout of the EGR system per alldata.
Is it worth attempting the upper O2sensor? Yes it would be but also it would be worth to clean out the upper intake with like Seafoam or Toyota's Top Engine Cleaning kit.
I cleaned the intake prior to installation on the rebuilt motor. How often does o2sensor effect NOX but not other emissions
It helps with fuel control but usually Nox is due to high combustion temperatures. Things like plugs, carbon buildup, egr flow all can contribute to high Nox readings.
Thats what i thought. So replacing 02sensor expensive. may not help at all. Should I put seafoam through the egr port on intake manifold. engine is too new for carbon buildup. how about retarding timing a few degrees?
Should I put seafoam through the egr port on intake manifold Yes/ Basically you will want to make sure that you are getting as much EGR flow as possible. how about retarding timing a few degrees? You can but only take it as far as is limited or needed but not too far as to effect other items.
Understand. Not much I didn't know but I will accept answers.
I won't but o2 sensor for now
buy not but