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nox failure

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wraenking, Feb 14, 2004.

  1. wraenking

    wraenking 1/2 ton status

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    hey guys. i have failed inspection 3 times for nox. i went from a 2900 readin to a 2400 reading after getting a new egr valve, pcv valve, and cad converter. is there anything else? im going nuts. a guy at a auto parts store told me to get a can of top engine cleaner?

    any help would be appreciated!!
     
  2. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    Nox is caused by high cylinder temps, carbon build-up could cause this, also, check your ignition timing
     
  3. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    Nox is caused by high cylinder temps, carbon build-up could cause this, also, check your ignition timing

    [/ QUOTE ]

    That's pretty much it. /forums/images/graemlins/thumb.gif
    When you changed the EGR did you clean the intake?
    Did you swap the CAT before changing the EGR?
    You could have contaminated the CAT with all the gunk in your system and now it's not doing it's job.
    But I would check timing first that makes a big difference. /forums/images/graemlins/deal.gif
     
  4. slider

    slider 1/2 ton status

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    Does your rig have an air pump? Is it working? I have used the top end cleaner it works well but if you really want the top end cleaned find someone who does Motorvac fuel injection cleaner. That system cleans from the intake track to the combustion chamber. We have had several rigs in that failed emission tests and cleaned their fuel systems with the Motorvac system and they all passed. This system can be used on carburated or fuel injected engines. NOx like others said is caused by high combustion chamber temps. Causes could be: Overheated engine, Lean fuel air mixture, Vacuum leaks, Overadvanced ignition timing, Defective EGR valve or defective EGR system, Too high compression caused by excessive carbon build up. I have had good luck with cleaning the fuel system, then retarding the timing about 4 degrees. After I pass the emission test crank up the timing back where it was. I hope this helps. Slider
     

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