Would a exhaust leak cause hi-nox?

[That1Guy]

I fail smog a couple days ago because my timing was off and I had hi-nox level. So I just the timing and it was retarded little too must and thought if it was retarded that much nox should be low. So I did a seafoam on the vacuum and I notice that smoke was come out near the header area close to the down pipe at. Is it possible for a leak before the cat to cause hi nox? I'm thinking the egr not circulating right.

[s13k1d]

iirc nox is only caused by high combustion temps.

[That1Guy]

But EGR help to low nox level. I know that already.

[s13k1d]

yes. that could be your problem. how bad did it fail by?

[asoomal]

My car failed the last emission test four times in a row with incredibly high NOx. Turns out the injectors were clogged... car ran fine though. I had them professionally cleaned (pressure) and it passed flawlessly.

[s13k1d]

My car failed the last emission test four times in a row with incredibly high NOx. Turns out the injectors were clogged... car ran fine though. I had them professionally cleaned (pressure) and it passed flawlessly.

thatll do it to. causes the motor to run lean. in turn higher combustion temps.

[That1Guy]

Think it was 550 max and it measure 860. just need to know if a leak before the cat would be the cause.

[s13k1d]

no if anything the leak will cause really high o2 levels.

[Wc240]

yes it can, but i doubt thats your problem

[CRyan]

mmmm. How I love living in a state that isn't worried about the ozone. LOL

[vancouverbc]

no. check the rubber hose that carries exhaust to bpt. it tends to rot.

240sx-egr-tutorial-t427162.html

[94_240sx]

Had high nox on mine too. Replaced a cat and passed with no problem. I'm just throwing another option.

[Wc240]

no. check the rubber hose that carries exhaust to bpt. it tends to rot.

l

true that is the most common failure on these, however thats only goin to fail nox on the 25 part of the test, not the 15.
what were the ppm on the 15 part of the test?