ZR-71

Mine passed smog in April. I looked at the test results to see the NOX measured but there is no measurement. The test printout says something about a visual/functional test is used to assist in identifying oxides of nitrogen, crankcase and cold start emissions which are not measured in the idle test.
Maybe Santa Cruz is not as strict on some measurements.
Wonder if you can get a test done in a different county than yours?

Z51JEFF

My car failed twice in the past,the Nox is what kills everybody.I went from 700 down to 303,the State max on Nox is 502,down from 702 a few years ago.I honestly dont know how the State can legally keep lowering the smog levels.Dave,we need to get together one of these days.

95ZR1

Very annoying, isn't it? And the CA smog website says they NEVER reduce the smog requirements.
Are you getting the "STAR" requirement? Harder to pay someone under the table,
but we wouldn't do that anyway, right?

From what I know, HC's go up if combustion (& exhaust) aren't hot enough which is what we are usually chasing.
High NOX is possibly from running TOO HOT. Assuming everything is working as it should,
this temperature balance is important.

You have a bunch of options. First, read the paperwork. They say take it to a mechanic/shop and see if something
needs to be fixed. They are older cars now and things deteriorate. I'm just leery that someone not trained or familiar
with the LT5 will mess things up. It could be something like the charcoal canister or spent cats, or you need maintenance
like new plugs, change your oil, etc. There are additives like "Pass Smog" you can try. You can enlist the help of a tuner
(Like Marc Haibeck) to deal with the specific area where you need the help.

Ultimately, you can go to a State Smog Referee and show them everything is as it should be. I've never had to go
this far.

Ask me how I know. It's an every 2 year PITA we have to deal with. For my car I have my "system" I do every 2 years
to pass legitimately. Good Luck!

mike100

My NOx was running high and it went down by almost half by changing out the O2 sensors. The formation of oxides of nitrogen is very sensitive to fuel mixture and if the O2 sensor is old and contaminated, even a 5% shift in accuracy will lead to a big change in NOx. They sensors are about $44 each at autozone for made in USA Bosch replacements (the oem German ones aren't made anymore- but no need, the ones you can buy now are good).

sal826

Well I tried smogging it again today - apparently the Gods liked me because I now PASSED!!. According to the report, my NOx score is now 391 and 364...

95ZR1

Congrats! Great feeling, huh?
Now go burn some rubber!

ZR-71

Congrats