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Another Emission?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by talison79, Feb 18, 2001.

  1. talison79

    talison79 1/2 ton status

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    I have looked over all the past posts on the board, and could not find the answer to my ? So here goes. I had the emissions tested today and failed again, same problem (oxides of nitrogen levels =NO). I just replaced the cat. It has about 10 miles on it. Completely stock rebuilt 79 350 with Q jet with all emissions stuff in place.
    My levels are
    __________ Reading _______Allowable
    HC-ppm _____ 11____________ 281
    CO-% _____ 0.00____________2.26
    NO-ppm ___3301 Fail_________1980
    CO+CO2%__14.5_____________ 6.0 min.

    This is a load test at 25mph. After I replaced the cat. Everything went down except the NO level, which is what the cat is supposed to also reduce. It went up from 2474 from a pre cat test to 3301. Just about everything under the hood is new about 2000 miles. Am I correct in thinking by running it lean for the test it is upping the combustion temp, thus causing the high levels of NO. I've got a good idea on how to fix it, just would like other input, and what better place to find it than here? Right, It's great to be able to pick brains from a distance. This is a great resource guys. Thanks for any input.
     
  2. Smitty

    Smitty 1/2 ton status

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    I'm trying to get a Blazer titled in my name and failed the test last week. I'm now labeled as a GROSS POLLUTER. It didn't help that the timing was 19 degrees BTDC when they did the test. I must have really messed up a few weeks ago because I checked it after I put the MSD unit in and had it right on. Threw the timing light on it right after the test and it was set at 19 degrees. I've fixed that and did a major tune-up on it. I'm weak on the emissions side of the house and could use any help that someone that deals with this stuff can provide.

    1982 Chevrolet Blazer, 5.7 Gas, Q-Jet, Auto Trans, Single Exhaust, Converter, MSD Ignition, Certification California

    ________%CO2__%O2__________HC (PPM)_________________CO (%)
    Test_____RPM___Meas___Meas____Max_____GP____Meas_____Max____GP____Meas_____Results
    Idle______799____11.2____3.5______120_____270____354_______1.50____3.00___2.20______Gross Polluter

    2500_____2374___13.9____1.4______150_____300____70________1.50____3.00___0.15______Pass
    RPM

    Max = Maximum Allowable Emissions GP = Gross Polluter Limits Meas = Amount Measured
     
  3. talison79

    talison79 1/2 ton status

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    Hay Smitty, have you checked your Idle mixture setting on the Q-jet? When I opened mine to check the needles they were out about 7 or 8 turns. I think you could lower your HC by retarding the timing, from normal setting, as far as reasonable and leaning out the idle mixture. I am in the same boat though, so me giving advice is like using your Jerry Springer appearance money to buy an engagement ring.
    If you are interested, here is a link to some really boring, but informative reading about emissions that may help. This is from the Air Resource Board in California. It explains what each part of the emissions system does and what year it was implemented.
    http:// www.arb.ca.gov/noxdoc/NOXDOC.HTM
    Hope this helps.
    Did you know they have a device that uses infrared light to check the emissions from a passing car in about one second?
    http:// www.theautochannel.com/news/date/19960403/news00445.html
    Hope this helps.
    Talison79
     
  4. blazercrazy

    blazercrazy Registered Member

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    If you can find RXP, pour that in a full gas tank and drive it around for about 30 min. You'll pass! It's a de-carbonizer and emissions reducer. RXP is out of Dallas, TX so you might not be able to find it. Any de-carbonizer and emissions reducer will to the trick. I've been in the same boat. I hate that damn test!

    Make sure your truck is the muddy one! [​IMG]
     
  5. talison79

    talison79 1/2 ton status

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    Sorry another question? I'm confused about full time 4 wheel drive. How the heck did they did they run my 79 with a 203 on a single rear dyno? The transfer case does work when shifted into hi lock and low lock. Has auto hubs that do work. I was waiting for it to drive off the dyno the first time but it didn't. I can't imagine the previous owners putting in a part time conversion. They didn't even change the spark plugs. What parts does the part time kit come with, or change so I can check it?
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Your hubs say "Auto" on them with 3-6 bolts holding them on?? Your K5 is converted then. A uncoverted full time K5 has a blank chrome hub cap over the end of the axle. http://grimsk5s.coloradok5.com/
     
  7. Smitty

    Smitty 1/2 ton status

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    Worried now. Got the new radiator in, hooked up a vacuum gauge,warmed the truck up and went to adjust the carb. Engine still runs with the mixture screws fully seated. Don't really want to pull this thing apart but might not have much choice. Any ideas out there? I'm starting to feel like I'm putting the cash into a bottomless pit!

    Smitty
     
  8. talison79

    talison79 1/2 ton status

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    Hey Grim sorry for the confusion, it just has the blank caps. When I said auto hubs I meant they engage when shifted into loc, no dial. That is what gets me. Its been run twice on the dyno for emissions tests. The first time I had It tested It was really early and my brain wasn't engaged yet, so I didn't think about it until it was already running on the rollers.
    Smitty the carb on mine will still run with the needles fully seated also, if it is running when I tighten them down. If I seat them then start the engine it will die. Don't know? You may lean out the choke and make sure its fully disengaged. But like I said mine will run fully seated and ran 11 out of 281 on HC test and a CO% of 0.00 with the needles out 3/4 of a turn out. Ran 134 out of 281on HC and 1.36 CO% with one turn out.
    Talison79
     
  9. Smitty

    Smitty 1/2 ton status

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    I've never had a carb run with the idle mixture screws fully seated unless there was a problem. I'll look it over today and see what's up. If I'm not mistaken the idle circuit gets it's fuel through the jets and if the idle mixture screws are fully seated there should be no fuel. It must be getting fuel from another source. I'm not real familiar with the Q-Jet but it doesn't really look too complicated, just hard to see with all of those vacuum lines running all over the place.

    I'll let you know what I find out.


    Smitty
     
  10. HarryH3

    HarryH3 1 ton status Author

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    Those "blank caps" mean that the front wheels are connected to the axles all the time. There is no lock/unlock feature, you're always in 4WD. The conversion kits for your setup replace the machined slugs under those chrome caps with real locking hubs. They also make it possible for the t-case to run in 2WD mode.

    The reason they can run your rig on the dyno is because there's a differential inside your transfer case. Think of a standard axle when one tire is on ice and the other is on pavement. Only the tire on the ice spins. The open differential lets all the power go to that wheel instead of the one on the pavement. The differential inside your t-case was doing the same thing. All the power was going to the wheels out back that were spinning on the dyno rollers. This is why your t-case has the "loc" positions. That locks out the differential for off-road driving conditions that require maximum traction. Othrewise you could get stuck and have power going to only one end of the rig. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://ThunderTruck.ColoradoK5.com>http://ThunderTruck.ColoradoK5.com</A>
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    I can't believe they can run them like that. I'd like to see one "accidentally" in 4 wheel drive when they try to do a 2 wheel dyno test. My state won't rear wheel dyno any 4wd truck. And as of yet, we don't have any 4 wheel dyno's, so it's idle and 2500rpm or so in park.

    That said, pretty sure the idle mix screws have nothing to do with the primary system. Totally seperate system. Somehow you are getting fuel through the primaries if those are closed off all the way, either that or someone swapped the idle mix screws on you. Yes running lean will cause high NO levels. Lean=Heat=high NO(NOx?) Is your EGR working by chance? That would have a large effect on it. Also is your new cat an exact duplicate of the old one? IE any pipes running to the old one are on the new one, etc? Also need to have the truck warmed up for the cat to work properly, so shutting it down right before testing is a bad idea.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  12. Smitty

    Smitty 1/2 ton status

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    Just guessing but I think the passages from the jets will lead into the primaries. I agree the fuel is coming from somewhere, just not sure where. Hadn't thought about someone switching the idle mixture screws. They might be grooved too.

    I checked the EGR valve and it's working fine. Went ahead and cleaned it up, was really suprised how clean it was. I'll let you know what I find when I open the carb up.

    Smitty
     
  13. dyeager535

    dyeager535 1 ton status Premium Member

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    Just checked last night...the fuelk is "sucked" through the idle system by engine vacuum. The primary system has no function at idel, as it (the power piston) is held shut by engine vacuum. HTH

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  14. Josh

    Josh Registered Member

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    Generally, high NOx is from high combustion temp in the chamber. This could be a lean mixture, EGR, and having the timeing either too far advanced or RETARDED. Both can cause excessive temperatures. Also ensure the coolant is doing it's job.
     

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