Emissions Test NOx Problem Plz Help!

[keruhas184]

Hello all,

I have a very direct question. I barely didn't pass the emission test with 3.7 NOx reading above the 3.0 reading.

Other readings: HC: 0.33 / (2.00 limit), CO: 2.57 / (30.00 limit). As you can see, my only problem is the NOx readings.

I have 87 lx accord, carbed. Two years ago NOx was 0.5. and other values were higher than now (this doesn't seem natural).

Then, I had high idle, and definately used 87 gas. I had my carb tuned not long ago and idle is way down and I used 93 gas. Is idle the problem?

I think I may need to add more O2 to the mixture, but not sure.

Main question: should I fill it with say 94, or 87 next time to lower the overall temepature (I think overheated mixture is the problem.) Or should I just fill the whole tank with Alcohol as it will not produce any NOx? Or should I use Hydrozine (if you have any let me know...)?

Is there some easy way to regulate the mixture to lower the NOx?

Please help, and thanks in advance for your response.

[AccordEXI]

I would check out the EGR system on the car. Make sure none of the lines are blocked with carbon, especially the one from the exhaust manifold to the EGR valve. I've had a blocked EGR cause a high NOx failure, while the rest of the readings were within spec.

[keruhas184]

thanks, I'll check it out

[87accordlxph]

Stick with the 93 on a carbed motor!!!

I have to go for an e-test as well.
Check the following:

EGR system including the valve.
Air injection system... does the car backfire as you gear down.
Cat Converter... does the exhaust smell like rotten eggs when it is warm any damage to it?
Plugs, Wires, ... tuned up your car?
Vaccume leaks?
Charcol cansiter... do you over fill your gas tank and plug this thing up?
Gas cap (very unlikely)
PCV valve work?

I think that's about it.

Good luck...oh no exhaust leaks???

-Mike from Sarnia!

[keruhas184]

93 is the highest I should go? not 94, not 98?

I actually found a bad spark plug, replaced it and it started to run much better.

On 93 I tried to pass again. Everything but the NOx came down even more. I will look into the EGR system now... as soon as I find where it is...

But I don't think I have any other problems. I just had the carb tuned, the muffler is all new except the Cat. but it should be good enough if other readings are so low...

but thanks for the help

[Mac]

A bad Cat could cause a high NOX reading. Also check the egr tube, it might need to be cleaned out.

[keruhas184]

Well, yeah, but I'm hoping it won't come to replacing the Cat. I was looking at some pics and the manual for the EGR system, and it is pretty ambiguous where to find it, as there are so many different models.

I will try to find it tomorrow, but does anyone have a clear pic of whre the EGR valve/system are at for:

Accord 87lx Carb, 4-door, manual model?

thanks guys, your advice has been great help

[keruhas184]

just a heads up for anyone having the same problem, a new EGR valve helped me pass, but barely. I think the old cat would be the culprit for bad NOx, but I got lucky and got by.

[98serwtricks]

How much was the valve and is it easy to R&R? My wife just failed emissions with the LX, haven't seen the print-out yet, but just trying to get ideas...

[86LXItooFAST4me]

have yall tried the quick fix for the test? go to a parts store and by this stuff thats 99.9% guaranteed to pass emissions. its a fuel additive. I forget the name but it works great.

[keruhas184]

yeah, i put that quick fix in too. But i don't think it'll be good on your engine down the road.

EGR = Exhaust Gas Recirculation (to cool the gas down before spitting it out) should not be more than $50 and is easy to install. The valve is right under the carb on the passenger side. I didn't see the installation (my dad did it), but it should be pretty straightforward. Use search and you should yeild more help on EGR.

[86LXItooFAST4me]

i understand that but i was just saying if you had to have it pass the test tomarrow, you could fix it next week. NAAMEAN?

[Blkblurr]

The old cat is what i suspect. The purpose of the cat is to reduce NOx emissions. By the way, for those of you that are putting higher octane fuel, it doesn't help anything to go to a higher octane unless you are having problems with pre ignition (knocking) Your compression isn't high enough to need it. The higer the octane, the more difficult it is to burn. This is a very common mis conception about octane ratings. Higher octane does not produce more power. It just allows the mixture to detonate when the spark plug fires and not before.