My Civic VX runs too lean...
 

That's not really a problem, but I can't seem to pass smog.
I live in the Bay Area (CA) and we live in the enhanced smog area, which means this area measures NOx. I pass all other tests with flying colors.

My smog results are as follows:

HC 9PPM pass!
CO .9% pass!
NOx 1600 PPM fail!

I have a 93 Civic VX CA model. Is there an easy way to richen up my car for smog testing?

I'm going to test again tommorrow or Tue. I just changed out my intake manifold hoping that would lover my Nox because the EGR passageway might be clogged. After taking it out, I tested the ports by pouring water in the EGR cleaning ports and it came out the runners slowly. On the new (used) intake manifold, the water follows throught the cleaning ports to the runners much faster. This should help with NOx.

i want to richen up the mixture to lower Nox (as you can see from the results, I am running lean - which I don't mind).

You vx'ers out there, what are your smog readings?

I love this car - I get 46-48 MPG. Not bad for a CA VX. I have to drive around 65mph or so to get that type of mileage. My best is 52 mpg, but I don't hit that milestone much.
Gary

New plugs just before you get tested may help.

I DO NOT recommend this next action as it may cause damage to your motor!
But one way to richen up the mixture and still pass visual inspection under the hood would be to unplug the vacuum hose running to the fuel pressure regulator and then break off the tip of a golf tee. Shove the tip of the golf tee into the vacuum hose, then push the vacuum hose back on the nipple on the intake manifold. What that will do is run the car at full rich. Only do this just before you get to the testing station and remove the Tee or swap out that hose for a regular one right after you get done testing. This more than likely won't work for the other tests though.

The Proper Way:
Replacing your Catalytic Converter will help reduce NOx levels.
THIS AUCTION would be the cheapest you can get a new compatible Catalytic Convert that would bolt up. I know it says for 96 and up, but the 92-95 VX is the same.

I pass smog two days after my original post!

Prev tests:

MPH HC CO NO
15 9 .02 1826
25 8 .02 1635

Latest's test

MPH HC CO NO
15 38 .09 185
25 19 .05 178

I cut my NO by 10 folds!!!

So, how did I do it?
Of order of importance, I think:

1. timing from 16 to 13-14 deg
2. clean EGR passageway by replacing intake with a known good one (I would put that as #1 but my intake was not completely clogged when I tested it)
3. cleaned carbon from intake ports on the engine and new intake (esp near the injectors)
4. new plugs - one step colder gapped at .041-.043; original one was probably 5 years old and had a gap of .60-.70 when taken out
5. New air filter (probably did nothing - I should have kept the old one in since old dirty filter will increase HC (which is what I want).
6. Cleaned EAVC (screen plugged) - not sure if this can affect NO

I went in early before temps hit 100 deg. Last time I warmed up the car for 30 minutes driving it on the highway. Not this time. I drove it to the test only station 5 mins away turned it off and waited. Engine cold when the guy arrived. This should be #3.5 .

My goal was to richen up the mixture somehow. I think retarding the timing did this, but not sure how it affects gas mileage. Since it's a commuter, I will probably advance it back to stock or higher.

NOTE: my gas mileage has gone down since retarding the timing. I'm getting about 41-42mpg. I just put it back to 16 deg tonight.

Anyways, this smog saga has come to a close for me. I spend so much time on it that I was getting frustrated and was wondering if it was worth it. Since I commute about 120 miles/day, I can say it was worth it.

Gary