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emission troubles

Discussion in '80-Series Tech' started by semlin, Feb 23, 2004.

  1. semlin

    semlin discouraged user

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    OK, so I finally got around to working on my EGR system this weekend. With much assistance and coffee from Riley, I cleaned the throttle body/plenum, replaced the modulator and VSV for EGR, cleared all hoses, then went back and failed the provincial emissions test again.

    Here are the before and after EGR repairs results (g/km)

    substance max allowable before after average
    HC 0.99 0.6756 0.6245 0.1655
    CO 12.43 9.9628 9.0036 2.6518
    NOX 1.55 5.3381 3.6388 1.4807

    So not much change. I have failed NOX twice and I'm still way above the average passing 93 80 on the other two (although I passed). My NOX did come down 33% but that might be due to the fact I was running a 10% ethanol blend 94 octane gas this time (supposed to reduce NOX emissions)

    Anyway, the emissions guy says with that high a result it must be the cats. He said don't waste time on the EGR. They see a lot of fails, and a lot of applications for exemptions where you have to detail repairs made to show $500 spent to get a free year.

    I have no codes and have checked the DLC to make sure it functions. My 93 has no 02 sensor behind the cats.

    So now I have a couple of choices. I can fix it or try and beat it. There is the "emissions pass" in a bottle option at the local auto places for $40. The local parts dealer said a litre of methyl hydrate in a quarter tank of gas will get you through, but you have to then fill the tank up right away. Does anyone know if this is bad for the engine?? I use that stuff as gas stablizer for my outboard fuel so I assume it can't be that bad?

    To fix it likely means new cats. I'm going to start a separate thread asking about this.
     
  2. landtank

    landtank SILVER Star

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    I can't be sure but I thought high NOX was a lean burn situation. Have you searched the web? If it is I'd look for a vacuum leak. I'll look around and reply if I find something.


    Looked around and found a site which indicated a dirty MAF sensor to cause a high NOX condition. You might try cleaning that before delving into the cats.
     
  3. ppc

    ppc M Go Blue

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    Have you checked for any MIL codes or have you just not seen the MIL on? If you jumper the proper terminals the light will flash consistently indicating no codes and the sytem working. You can have stored codes without the light going on.

    I would do some reading specifically at the following link: http://www.autoshop101.com/forms/h64.pdf It talks about how the converter works and what possible causes for problems. Your converter may be bad but that is a symptom and not the root cause. Your NOX is high but HC and CO is as well which indicates fuel delivery and O2 sensors.

    Backup to http://www.autoshop101.com/autoshop15.html for other topics that are related. Overall good reading.
     
  4. Shortbus

    Shortbus

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    Not sure if this is helpful at all, but.....

    I tried to chase down a similar problem in an Audi, and it turned out to be a timing issue. I know VERY little about tuning the LC engine, but might be worth a quick look?!? On the Audi, it dropped the HC from 998 ppm to 68 ppm.

    The other thought was adding Methanol. You'd have to do a little searching to see what the proper mix is. When I was working for Goodyear in Sacramento, we used to have some "smog challenged" cars. The Methanol mix would get most thru. But, you've gotta be careful with the mix, so not to grenade the engine. Use that little trick with caution.

    I've never tried it, but CRC makes a product called "Guaranteed to pass" which is supposed to be pretty good. Don't remember it being quite as expensive as the stuff you mentioned.
    [​IMG]
     
  5. semlin

    semlin discouraged user

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    Phil, I have checked and there are no codes -- I get the flashing light. I will do some reading as you suggest.

    Shortbus, yup that's the guaranteed to pass stuff they sell here too. The price here is Canadian.
     
  6. e9999

    e9999 You want to do what...? Moderator

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    ads to beat the system - guaranteed... ?
    only in (N.) America! :)
    yeah for free market (still the case in Canada? :D)
    E
     
  7. xl715

    xl715

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    NOx is caused by high combustion temps, the higher the temps, the higher the NOx. It's a by product of buring gasoline at extreamlly high temps. EGR flow helps reduce NOx emmisions by lowering chamber temps. The amount of heat an engine develops is directly related to how much fuel is burned. The amount of fuel burned is directly related to how much oxegen enters the engine. EGR purges to allow exhaust gas to take up some of the room in the combustion chamber, being an inert gas it won't burn and thus keeps NOx down by keeping temps down.
    NOx is also an indication of a lean burn, however all your levels are fairly high, so it may just as well be a catalitic converter issue. If you have a temp gun you can check temps on both sides of the cat, you should have reading of about 100 degrees difference front to back if the cat is working properly.
    Did your reading give you an oxegen content or a nitrogen content, would help diognose a little further.
     
  8. robbie

    robbie Guest

    After not finding any problems with anything on a few customers trucks I replace the O2 sensors and that cured the problem and they passed emissions. My cats are still working at 217kmiles enough to pass denvers emissions testing and the imposed NOX decress last year. after rebuild I put in new O2 sensors to start fresh.later Robbie
     
  9. Gumby

    Gumby Supamod Staff Member s-Moderator

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    My EGR isn't working (P0401) and my rear cat doesn't work. Passed on all gasses with no problem. IL can't dyno an AWD, maybe that's the difference.