# 1996 Nissan Altima failed smog



## Clubwise (Jan 3, 2010)

Topic.

My 1996 Nissan Altima failed smog during the 15mph hydrocarbon test (i used this to justify my speeding to my fiance, declaring it was better for the environment, try it, it kinda works  ). Passed everything else. The car is mechanically sound, does anyone have a direction I should go to try to figure out the issue? I need my car and I can't afford a mechanic to diagnose it (damn you economy...)

It's a cali car if that makes any difference at all.


----------



## rogoman (Dec 16, 2004)

Here are some items that could be causing a high CO reading:
- Dirty air filter.
- Dirty spark plugs.
- Incorrect ignition timing.
- High fuel pressure.
- Dirty fuel injectors, leaking injector(s).

Change the motor oil before going for another smog check.


----------



## jserrano (Oct 27, 2004)

He failed for high HC not CO.


----------



## rogoman (Dec 16, 2004)

Sorry , I meant to say high HC. My mistake.


----------



## mc60170 (Jul 13, 2006)

*Failed Inpection High HC Hydrocarbon Levels*

I too just failed the NYC/NYS emissions test for High HC levels. My vehicle read 0.83 gpm and the test limit is 0.80 gpm.

I recently changed the plugs, wires, distributor cap, rotor, and air filter. I have noticed that my mileage has been down over the last couple of weeks and that while driving on the highway the check engine light will sometimes come on for about 30 seconds and then go off.

Could the air/fuel mixture be too rich? What would I do about that? Any other ideas? I am trying to figure out what to do next.

Thanks,
Marc:waving::waving:


----------



## mc60170 (Jul 13, 2006)

For anyone following, I did get my car through inspection. Did a mini tune up, replaced the plugs with NGK Platinums after gapping. Ran a tank of Techron through the vehicle. Brought it back for an inspection...it failed, then the mechanic re-ran the test with the heater on full and it passed. Doesn't make an sense to me, but I was very happy to get the sticker. Anyone have any ideas why running the heater might affect the outcome of the HC emmisions?


----------

