Just had my 95 e320 wagon at the Arizona smog station and barely failed by .01%

Unbelievable!

First test gave readings as follows:

HC: 0.23 Applicable standard.......0.80

CO: 5.91 " .......12.00

NOX: 2.10 " .......2.00

Passed HC and CO but failed NOX by .10%

I cleaned the EGR, reamed the EGR tube and put in a new set of Bosch spark plugs.

On the second test the readings dropped.

HC: 0.16

CO: 4.05

NOX: 2.01

So everything improved but that .01 difference in NOX failed me!

Help!!!

Thanks in advance for your valuable suggestions.

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I have never met a man so ignorant that I couldn't learn something from him. -Galileo Galilei, physicist and astronomer (1564-1642)

The air/fuel mixture needs to be enriched a bit, it's a balancing act between HC and NOX. You have lots of room for HC to go up so NOX can come down. When did you last replace the oxygen sensor?

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Suppose you were an idiot, and suppose you were a member of Congress; but I repeat myself. - Twain

O2sensor was replaced about three years ago ... mileage since about 50,000.

I've had this car about ten years and it has never failed it's biannual smog test.

How do I enrich the air fuel mixture?

__________________
I have never met a man so ignorant that I couldn't learn something from him. -Galileo Galilei, physicist and astronomer (1564-1642)

Make sure you go over the entire EGR system.

The EGR circulates some exhaust into the intake, which helps lower combustion temperatures by several hundred degrees. High combustion temps create NOX, so if your EGR isn't operating at or near 100%, it could explain your test results.
https://en.wikipedia.org/wiki/Exhaust_gas_recirculation

__________________
Suppose you were an idiot, and suppose you were a member of Congress; but I repeat myself. - Twain