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high NOx

Discussion in 'The Garage' started by TheEmissary, Apr 28, 2004.

  1. TheEmissary

    TheEmissary Registered Member

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    I have returned home form the testing faciliyt this afternoon, and noticed that my NOx levels have risen, right after the carb was rebuilt. Here's the test results:

    HC: 281 (111 25 mph)
    CO: 2.26 (0.02 25 mph)
    NOx: 1980 (2318 25 mph)

    I have been through 4 emission tests - I am more concerned of getting a bootleg sticker or face a $200 fine if pulled over from the cops.

    If this is not over - I will be forced to retire the vehicle the the salvage yard or to another county which does not do emission testing; or donate the vehicle to the ArtCar Museum off Heights Blvd. in Houston, TX. for 2 years. Otherwise, I will pay $120 for a METRORail pass.
     
  2. bigyellowjimmy

    bigyellowjimmy 1/2 ton status

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    Did you replace your cat? (I cant remember) Your HC's are much higher than mine with no cat and your CO is about the same.

    Does anyone know what would cause these high readings?
     
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Have you checked your ignition timing? Is your EGR on and functional?

    As mentioned before, do you have a cat?
     
  4. unclematty

    unclematty 1/2 ton status

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    I've been a tune up tech for a long time (10+ years) thats got to be your EGR valve, a cat will not reduce NOX. 1 apply vacuum to the valve, it should open while holding vacuum pressure, 2 it should hold vacuum pressure, 3it should close whenvacuum is released, 4 attach a vacuum hose to the valve and to a PORTED vacuum port on the carb.
    PORTED= vacumm applied only during moderate to heavy acceleration, ??? email me!! /forums/images/graemlins/waytogo.gif /forums/images/graemlins/hack.gif /forums/images/graemlins/weld.gif /forums/images/graemlins/grind.gif
     
  5. Smitty

    Smitty 1/2 ton status

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    Make sure the EGR ports in the intake aren't plugged with carbon. I've seen a lot of these plugged solid.
     
  6. 4xcrazy

    4xcrazy 3/4 ton status

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    YUP /forums/images/graemlins/waytogo.gif NOx = EGR valve
     
  7. TheEmissary

    TheEmissary Registered Member

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    I was road-testing the M.P. this evening on State Highway 288 in Brazoria County; I started with a 12* BTDC baseline. I lowered the static timing to 8* BTDC, and during a pit stop in Lake Jackson, I set the base timing to 6* BTDC.

    When I connected the EGR valve (with the static timing set @ 8* BTDC), there was a lot of surging as if my art vehicle was a Chevette. The EGR valve which I dropped in came from my old 305 - it still functions depsite testing with a Mityvac pump.

    I finally drove to the Montrose in H-Town (keep in mind that I am a Str8-But-Not-Narrow mekber of Colorado K5) and noticed that the accelaratoin was more responsive right after I adjusted the APT valve (see previous postings under failed emissions in H-town).

    If anyone bothered to catch the pic of my vehicle - here's the link:

    http://houston.indymedia.org/news/2004/04/28142_comment.php#28144

    I hope that CK5 members would consider the pic as a sacrilege.
     
  8. unclematty

    unclematty 1/2 ton status

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    surging means it ,the EGR, is open, when its not suppossed to be. so, get the right EGR, and install it correctly.
    I'd bet that the EGR you installed is the wrong one. they all open at different times and different amounts. /forums/images/graemlins/waytogo.gif /forums/images/graemlins/hack.gif /forums/images/graemlins/weld.gif /forums/images/graemlins/grind.gif
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    6* is probably too much timing, too. Advancing your timing, although it typically will make your engine run better, increases emissions.

    Retard it to 2-4* and it will help with HC, I'm sure.
     
  10. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    NOx is caused by heat and pressure. It could be a few things, timing, as mentioned, high compression, lean mixture, cat, EGR, closed thermostat. I dont know about Texas, but here in CA your timing can only be 3* above or below the MNFGs spec, that is, if a limit is not specified. Id check to see if the EGR is working properly and if so , clean out all the carbon.
     
  11. Triaged

    Triaged 1/2 ton status

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    Using higher octane gas will lower your Nox as well.
     

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