I have an '87 5.0 Iroc, 5sp. It has 170K and has never been rebuilt. It just failed the Connecticut Emissions test (by about 50 PPM)for NO (Nitrous Oxides). It passed the Hydrocarbon test no probem. The car is stock and I just regapped the spark plugs and replaced the wires and rotor. (by the way thanks everyone for the help, my eradic tach and ignition problem was totally solved by replacing these.
My question is are there any things I can do to lower this number?? Could detarding the timing help? When I regapped the plug wires they were white, indicating too much advance, but this may have been due to the failing ignition system (also found loose sparkplugs, dealers fault-long story). The car is running perfect now, starting well.
Thanks for any help.

 

High NOx emissions are usually generated under high combustion temperature conditions.
Lean mixtures, over-advanced ignition timing and high engine temperatures all contribute to high NOx.
First, check the operation of your EGR valve. It's only function is to cool combustion temperatures by injecting exhasust gases, reducing NOx.
Check that your timing is not too far advanced and that your mixture is not too lean.

 

drive till you have like no gas int he tank and put in about 8-10 bottles of gas antifreze you'll pass then.

 

didnt the smog tech tell you what exactly the problem was. in california, where i failed my smog the first time, he told me my EGR valve was bad. it was a fairly easy fix. ask him what exactly was holding you back.

daniel

 

I'm also thinking EGR.. especially since your HC and CO numbers were normal- and those two indicate a rich/lean running condition.

Also, what about the catalytic convertor? The newer 3-way versions also "treat" NOx's. "Supposedly" thru the AIR pump's intervention, by it pumping fresh O2 into the cat, NOx is converted to NO2, and CO to CO2.

I still believe that the AIR pump is a farce, and just dilutes the exhaust mixture (why pump fresh O2 into the exhaust, when the exhaust will see fresh O2 after the tailpipe anyway??), but that's another story.

Check out your local auto parts store for something called "Emissions Test" or "Rotten Egg Smell Eliminator" or "Guaranteed to Pass (G2P)". I used the latter one, and passed with flying colors. Those supposed to clean out your catalytic convertor somehow.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards

 

The air pump puts fresh air in at the manifold where it is still hot. By injecting oxygen into the exhaust it causes it to burn again because there is still unburned fuel (HC's) in the exhaust. If you waited untill it got to the tailpipe it would have cooled too much and would not ignite.