Drove around for along time after the O2 rewire and no MIL. Went to the shop where I had failed emissions and they just hooked it up in testing mode and reved the car for a while.

HC and Co looked good but the NOx was high... about 5.0 with the limit at 2.0.. Previous test was at .64

EGR valve? Any ideas here? Does it only work under load? BTW, I have a random tech cat with about 8-10k miles on it.

 

Modern car designs use two strategies to to reduce NOX.

1) Avoid creating NOX.
This is the job of the Exhaust Gas Recirculation valve.

2) Convert the NOX to less harmful chemicals.
This is the job of the Catalytic Converters.

Does your Maxima have an aftermarket Y-pipe? Installing a Y-pipe probably eliminated two small "pre-Cats", and that hurts you at smog test time.

 

His, homepage says he has an aftermarket, B-pipe, and a Y pipe, with a 2000 maxima SE muffler... mabe this will be able to give you a better Diosintic Db martin

 

Nox went up because your a/f mixture got leaner. When the car is running rich, the combustion temp is colder. Nox is created by higher combustion temp.

I tested a rt cat on my car and it only reduced hc by 140ppm max. Other generic non high flow cats can easily reduce it by 3-4 hundred. In my area, we don't test nox so I don't know exaxtly how well the rt does for nox. I'm guessing not very well.

Egr system is pretty east to check. No tools are needed. Put your fingers under the valve and slightly touch the diaphram?. Rev the engine and you should feel the diaphram move up and down. Now at idle, push the diaphram up and the engine should cut off.

 

Ouch.

 

Where is the valve/EGR?

SuDZ