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Failed CA Smog Test - 92 740T 700

posted by  kilbrid3 on  Sat Feb 18 12:58 CST 2006
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Hi All,

I just failed this years smog test because of NOx. The car has 180K, and runs well. The test is on a dyno. In preparation for the test I did the following:
plugs, fuel filter, new thermostat, cleaned the TB, ran some top end cleaner through to knock any carbon out, replaced any suspect vac. hoses, premium fuel in the tank and a fresh oil change 5 miles prior to test.

The test results as follows:

15 MPH 1738 RPM
%Co2: 14.5
%02: .3
HC: Meas 77 Max 114 Ave 31
CO%: Meas.48 Max .73 Ave .1
NOx: Meas 1007 Max 785 Ave 237

25 MPH 1755 RPM
%Co2: 14.5
%02: .3
HC: Meas 71 Max 88 Ave 20
CO%: Meas .51 Max .61 Ave .09
NOx: Meas 848 Max 724 Ave 199

I have read most of the FAQs and posts. Any thoughts out there. The car has the original O2 sensor and CAT. I would like to know if there is anything else I can do before I start throwing money at it. I don't think my multimeter is sensitive enought to check the O2 sensor.

Any help would be great!

Thanks,

Bill







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    Failed CA Smog Test - 92 740T 700

    posted by  Greg Hebert on  Wed Feb 22 05:17 CST 2006
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    last visit: Tue Sep 22 08:17 CST 2009
    [RELATED]

    Hi There,

    I'm not sure if you resolved this with the blocked EGR tube, but I went through this and discoved only later that my rear calipers were frozen and definately dragging. As my car 1986 is 20 years old now, I was able to get my sticker in Ontario as of Jan 1, 2006 (I was less than 2% over the limit after 3 tries last year).

    After noticing the great improvement in driving/gas usage after the brake repair, I wondered if sticky calipers COULD affect the in gear 'Drive Test'. My idle numbers were great, although they do not measure NOx for that portion here.

    Just a thought...

    Greg








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    Failed CA Smog Test - 92 740T 700

    posted by  Volvos4me4ever on  Tue Feb 21 06:35 CST 2006
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    last visit: Fri Mar 23 07:32 CST 2007
    [RELATED]

    I have an 89 245 non-turbo and I failed emissions almost the same as your 740T did. Checked a bunch of things and swapped some stuff that I had spare used parts for. One of the 240 members suggested replaceing the Coolent Temp Sensor. I had a used one of those so I figured it was worth a shot. Was a real pain to replace it (3.5 hours of back breaking work) as the CTS is between the 3rd and 4th cylinders under the intake manifold. After replaceing the CTS my HC & C0 was next to none and NOX was low as well. If you got HC & C0 readings over 70 & 50 then swapping the Cat won't help you much and cost you some $$$. My 245 MPG was better as well after changing the CTS and it's running much better.

    My 245 has over 279K miles and has the original engine and Cat. Converter...

    There's my two cents...

    Best of luck...
    --
    Volvos4me4ever 1989 245 278K miles still going strong, 1992 745 Turbo 121K miles real nice!








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    You probably need to replace the cat 700

    posted by  Ken C on  Sun Feb 19 16:52 CST 2006
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    last visit: Fri Oct 24 11:39 CST 2014
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    Folks on the 200 forum report, when they only fail NOx, that changing the cat really fixes up the readings.

    Good luck.







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      You probably need to replace the cat 700

      posted by  Rule 308 on  Mon Feb 20 04:48 CST 2006
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      last visit: Tue May 8 09:20 CST 2012
      [RELATED]

      Take a look at your numbers, although not failing in all catagories your numbers are high across the board. You definitely would benefit from a cat but I would check out the O2 sensor as well. It should have a rise time of 100 milliseconds, it should be able to sweep from 0-.9 volts in 1/10 of a second. If it fails to drop all the way to 0 or go all the way up to .9 or it cannot do it in the specified time frame then you have what is reffered to as a slow or "lazy" O2 sensor. If you do not have the equipment necessary to diagnose it then you might want to look into just replacing it with a new Bosch sensor and move on. A new cat and a new O2 sensor will usually fix a car but often times the vehicle will have other problems and the cat and sensor will simply mask the problem long enough for it to get through the inspection and then the new cat will fail shortly thereafter from having to much crap and crud run through it. This is what we in the industry refer to as a "clean for a day" repair. The numbers you are posting do not indicate that you have a problem elsewhere but without actually seeing the car it is impossible to tell. The catalytic converter is simply meant to clean up a slightly rich condition, it is not a garbage disposal unit and using it as one will greatly shorten it's effective lifespan.

      Mark








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        You probably need to replace the cat 700

        posted by  kilbrid3 on  Mon Feb 20 09:33 CST 2006
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        Thanks All for you thoughts!

        Here is the status. I went through the EGR system - pulled it all apart. I found something interesting. The tube coming from the EGR valve to the intake manifold was 80+ percent blocked. It must have to do with the hard turn in takes at the top. The rest of the system is clear. The valve functions well, and holds vacuum. The vacuum booster passes the onboard diagnositcs. I cleaned everything and put it back together.

        While I was in there, I cleaned the breather box, and replaced the old cooked 0-ring that seals it to the block.

        Since I have a free retest, and the EGR blockage could be a root cause for the high nox, I going to give it another try. I will keep you posted.

        If this does not do it, I will go with the o2 sensor and cat.

        thanks,

        Bill







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