HELP!!! What controls Nox levels? 92' 2.3l

[tommyg25]

I just failed my emissions test for the second time, now everything is a pass except for the NOx (it's about 4 times the passable limit), It's a 92' 2.3l. and runs great, I thought EGR, but it dosen't have one. So what controls the NOx level?????.............any help would be great.
Thanks

[skibum1111]

If you are not getting a check engine light, your cat might be bad, has it been hollowed out?

[tommyg25]

Originally Posted by skibum1111

If you are not getting a check engine light, your cat might be bad, has it been hollowed out?

But, then why would HC, and CO levels be good????

[skibum1111]

Ok, i'm stumped.. dirty air filter, dirty throttle body, maf sensor? I'm reaching here....

[Hoags]

Here's an old trick that used to work,(so I'm told) Schedule your emmissions test but before you go fill the tank with premium gas and get the car up to operating temp. This used to work on the older cars in PA. (I do not know if it really works, I have heard from several people that said they have done it and their car passed the emmission test. That was a few years ago, I don't know it the testing equipment is more sensitive than it used to be.) I wish I could asy for sure that this works, but it does seem to make a little sense that a higher grade of gas will burn cleaner and may be enough to pass the test. I have also heard of guys using an octane booster just before the test, again I do not have first hand knowledge, just what I have been told.
You can take this for what ever it's worth. Like I say, I've been told it works but that was a while back, all I can say is that a higher grade of gas or an octane booster is not going to hurt anything with the exception of your wallet. Gas is way too expensive even for the regular.
Hopefully someone else on the forum can either help you with a mechanical explanation of maybe verify the high grade gas/octane booster trick.
Good luck!

[BNaylor]

I agree with Hoags but here's another suggestion.

High NOx is a byproduct when nitrogen and oxygen in the air react due to high temperatures. The higher the temp., the more NOx is developed. The object is to reduce peak combustion temperatures which will reduce NOx.

Thats the purpose of an EGR but in your case you don't have one.

On the other hand high HC and CO would be the result of incomplete combustion of the fuel. This reading is normal so the CAT is probably working OK and other engine parameters such as ignition and fuel are OK.

Another suggestion would be to make sure your cooling system is working at optimum. You could put in a lower temperature thermostat (160 - 180 degrees). And try running one or two range colder spark plugs. Good luck!





Thrasher CAI, DHP v1.0 ECU,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, TB spacer,
MSD 8.5mm wires, Autolite 104 Spark Plugs,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[BNaylor]

BTW - I forget to mention most GMs use a 3 Way CAT convertor. Since your NOx levels are very high you might consider the CAT convertor if all else fails. The first stage of a 3 way CAT is the "reduction" catalyst. It uses platinum and rhodium to help reduce NOx at the molecular level. The second and third stages reduce HC and CO.

That might explain how NOx is reduced in your specific engine and model without an EGR.




Thrasher CAI, DHP v1.0 ECU,
3.25 SC pulley, CAIT GMAF, Hi-Flow CAT,
u-bend delete, 160 TS, TB spacer,
MSD 8.5mm wires, Autolite 104 Spark Plugs,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials[/quote]

[dongb]

i passed all on my emission test ecept to high NOx can someone help 5.7 liter engine

[Ridenour]

Welcome to the forum. From now on, make a new thread instead of reviving an old one. Also, you need to start the thread in the forum related to your vehicle.