Slightly High NOx

So here in CO we just adopted new standards on NOx, went to get my 2000 tested, and barely failed (would've passed the old standards). Any ideas on how to slightly lower? the HC and CO readings were easy pass/pretty low.

I get this indicates a potential slightly lean condition / high combust temps. Recently changed timing belt (AISIN Kit) and sparkplugs/wires (Denso/NGK) - not sure if that influences, as it doesn't appear that you can manually advance/retard timing and no EGR on the V6.

Truly need to slightly lower, was running 85 octane gas, would higher octane help? Any can't miss additives? current plan is to burn it up and down the highway for about 30 minutes and add a bottle of ISO Heet then go straight to the tester - any other ideas?

EDIT - no codes being thrown

 

wtf is nox

 

Nitrogen oxides

 

What did you do? Went for my smog check (every 2 years) All of a sudden, I'm a "gross polluter," the 15 mph test for NOX was 2796 ppm. The 25 mph test was only 46 ppm...Labor rate was $105, so I'll get out the toobox and start checking

 

That sucks, even here (LA county in CA), 2000 model years and up don't have to get dyno/sniff tested. Just an OBDII scan and visual inspection.

Could try a bottle of that Cataclean stuff, supposed to help with that kind of thing.

otherwise maybe hook up a scanner and see what your fuel trims are like, could help point in the direction of what needs addressing.

 

Is there no grandfathering in for older model year vehicles? What happens if you can't reduce your nox, you have to get a new car?

 

Older cars aren't held to the same smog standards as newer ones but they still do have to pass a certain level of inspection. Unless they're older than 1975 then they're exempt entirely (talking about CA here). You can be 'waived' from smog tests if you've failed twice and can prove you've spent a certain amount of time and money on getting repairs done that didn't work out. Sounds like it's a crapshoot though. I think in most cases people just end up getting a different vehicle.

in CA though <2000 has to go through the headache of the dyno and tailpipe emissions tests, newer doesn't thankfully

 

My smog papers say I'm a gross polluter also but isn't this because some truck years were exempt from strict smog standards by design and even SUV's got rolled into that? My truck is CA and no EGR, no pre cat, no air pump - every car I have owned has all of that and more.

I have to do the dyno test too and there are not many around, one smog station owner told me he loses money on it.

 

I think the gross polluter label is given to any vehicle that fails the tailpipe emissions test with certain levels of emissions. But they won't hold a vehicle with less smog equipment to the same testing standards that they hold more modern vehicles to, that wouldn't be fair (pretty much why older than 1975 is exempt because they have no smog equipment).

yeah I imagine as time goes on there will be less and less stations that will be willing to test older vehicles. The place I go to has a dyno for testing older cars but it's a pretty small 1 man shop

 

What are your current readings? Also, what is your current o2 content? You need to post up your readings so I can see it.

This either cooks down to a poorly working EGR setup due to restricted passages or stuck diaphragm, or the catalytic converter, but without seeing what you are at and without your willingness to do some testing on your end (if you have the means and resources) we can't really do much to help you.

 

Just wanted to inform the wary . I did my own inspection (which I should have done in the first place!). I had some split hoses in the lines to the evap system, all located on top of the intake manifold
: ) I replaced the split (right at the hard line) to the manifold from the evap box, and I replaced all the clamps with SS-clamps that tighten with a nut/screwdriver. I inspected the line all the way to the fuel tank. New line from the intake to the PCV valve (after checking the valve ). I replaced the clamps on ANY hose that connected to the intake manifold. Passed easily...

The truck was not running bad at all prior to this, but it now runs a bit stronger, and idles very well.

 

Let me add that I used a soap solution in a spray bottle to pinpoint the leaking sites: bubbles are what you don't want to see!!

 

Im in the same boat they lowered the limits in colorado this year and squeeked by on the Nox. To the op did anything help did it pass at all. I heard cleaning MAF helps. Heres my results. Also I heard if you use the highway sniffers the year before usually passes.

limits readings

.80 .29 HC
15.00 4.22 CO
1.50 1.4911 Nox

 

Unfortunately no, none of the additives or isoheat BS worked, then my Catalytic converter ended up getting stolen - and I had to get a new one. Haven’t tried since as it’s not due until Feb, but I’ve got to imagine I’ll pass now

I also think driving past the auto sniffers a bunch is probably the way to go

 

I have been looking online and it looks like maybe front o2 sensors or cat.

 

Probably, o2 is any easy fix, actually was going to be my next attempt before the cat got stolen. I will say I had no codes being thrown but when testing with my obd scanner I could never get the Cat to “ready” - after a new Cat and new o2s it readies.

 

So a quick update. Nothing has changed in my tacoma as far as just regular maintenance. In Colorado we have 10-15 percent ethanol gas at the pump for better emmisons to the environment. We also have stations that have non-ethanol gas. Although it is expensive I decided to switch to it 2 years ago and my Nox has gone down .5. Has no problems passing and the truck runs so much better.