The old monster passed again. All flying colors with wide margins, except for the 15mpg NO -- was right at the 550ppm (I'm guessing from memory) maximum. 25mpg was well under that limit.
Outside of major replacements, what would bring NO down?
NOX goes up as combustion temp goes up. If your EGR is not working your Nox goes up. If the wrong thermostat (too hot) is installed, NOX goes up. If the rad is bad, raising operating temps, the NOX goes up. If timing is too far advanced, the NOX goes up. If the engine is running too lean, NOX goes up, and of course, if the catalytic converter reduction bed is failing, NOX out the pipe will also be high.
except for the 15mpg NO -- was right at the 550ppm (I'm guessing from memory) maximum. 25mpg was well under that limit.
Thanks. What would make NOX run so much higher at 15mph and not 25mph?
My first thought would be a restricted EGR system. Take off the EGR valve and tubing and clean out all the carbon from the system.
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