have a silverado 4.3 the emissions test failed my vehicle because of
HIGH LEVELS OF NITROGEN OXIDE what can I do to correct this problem thanks in advance....

 

nitrous? do you have a nitrous kit on your truck or something?

 

whoops sorry i read that wrong. how bad are the cat converters?

 

Hey bro,

Couple of things here. Stopspazinout could quite possibly be right here. First of all I am going assume that when it comes to an emissions test that your vehicle failed the term of Nitrogen Oxide you say should be NOx. NOx in california is created from a couple of things. A Catalytic converter is typically designed to burn off unburnt fuel that comes out of the engine which comes out of the tailpipe in the form of HC or Hydrocarbons. So before you go replacing the cat first thing to do to check it would be to take a infared thermometer to it(Laser temp gun) and see if it is hotter in the front of the cat than in the back. If not your cat is shot.

Two things that will contribute to high NOx would severly advanced timing if you have a vehicle with a distributor than you can easily check the timing, you should be able to check this with a timing light and the instructions should be on the underhood label.

Other thing would be an EGR valve being faulty or not actuated or quite simply clogged. Ifyour egr valve is vacuum actuated you will want to take the vacuum hose off of the inlet nipple with the engine running and put your finger over the vacuum line, raise the engine rpm a few hundred rpm. If you feel no vacuum than this is where the problem lies you have a wrong vacuum line hooked up. Egr valves need to be hooked up to ported vacuum not manifold vacuum.

If your Egr Valve is is electronically controlled you will want to see if the valve itself is physically clogged. This would obviously require removal of the valve. It is very easy to remove the valve usually 2-3 bolts. If you are going to take the time to remove the valve you will want to get a Egr Valve cleaning tool. It does not clean the valve itself but the passage where the valve hooks up to. This tool is usually about 15.00-20.00 and hooks to a drill. It looks basically like a plumbing snake with a drill bit on it. If you can find one it is worth the price of admission. I used to charge an hour of shop labor to clean out this passage. Hopefully this helped.

 

Nox high= bad egr