CA smog fail high nitrous oxide
 

Just did smog on my 88 NA every test is good besides the NO (PPM) at 15mph MAX:565 MEASURED:812. At 25 mph it passed but barely MAX:522 MEASURED:496. Any clues what is wrong here? I do smell lots of fuel maybe my injectors are the problem . I'd rather do it myself than to take it to a shop.

Was your cat hot? Ignition timing to spec?

High Nox (oxides of nitrogen) emissions are usually indicative of a malfunctioning egr system, I'd probably start troubleshooting there.

Rotaries are naturally quite low on Nox. The EGR was not really necessary and even removed on the S5 FC.

I have failed for high Nox due to a vacuum leak. It was because one small vac hose was not connected.

i had one that failed Nox due to a bad 02 sensor. there is a test port, and you can plug an LED into it, and watch the o2 cycle, or not in my case. new 02, and car passed easily

nox's started @800, retarding timing 10 degrees (back to stock) took 150 nox's off. then the o2 sensor took another 500 off or something

NOx in our cars is caused by running very lean or having excessive timing advance. You are a thousand times more likely to fail due to HC than NOx.

i've smogged something like 100 rotaries at this point, and only failed Nox once, because it was lean. timing does effect nox too, but its fairly minor

Vacuum test acv. Diaphragm probably failed. Able to shim the acv to always be open. Search.

Vacuum leak possible

Clearly your intake manifold has failed.

http://www.autolifers.com/wp-content...3/image_3.jpeg

Im having same problem, 1st, engine light didnt work on the idiotlight, so i used one next to it that worked.......then they did the actual text and failed horribly, they told me i needed new converter and they needed to see the eo number on it......
ok went out and had a new converter put in
back to smog...did the test and failed again---this time they are telling me its running too lean, and i might need to get an o2 sensor, or check my fuel filter......
I have a 1990 rx7 n/a

i would check to make sure the Air Control Valve (ACV) is working, it is more important to emissions than just about anything else

I agree with this.

A bad o2 would make you run richer, not leaner.

i had one with a bad O2, and it ran lean and failed NOX. although i think rich is more common. there is a test port you can plug an LED into and watch the o2 cycle

For what it's worth, increased NOx emissions is the result of combustion chamber temperatures being too high. Aim your diagnostics/repairs in the direction of reducing combustion temps, and you'll be headed in the right direction.