1995 Saturn SL1 fail Emissions Test for high NOx

Discussion in 'Saturn S-series' started by Roger E, Nov 25, 2008.

  1. Roger E

    Roger E Guest

    1995 Saturn SL1 fail Emissions Test for high NOx

    Car: 1995 Saturn SL1 SOHC, 1.9L.

    Symptom: Drive Clean Emissions Inspection Report show failed reading for
    NO ppm:

    Another headache.... ok my Saturn is 14 years old, so things are bound
    to fail on it.

    I’ve included my last three Emissions Tests results below, (done every 2
    years). In 2006 my NOx result was a close pass. In 2008 the result for
    NOx was a bad fail. However the HC and CO measurements have not been a

    The info included suggests for high NOx on driving test...

    1.-inoperative EGR... my EGR valve is fine, not the original, I did
    replace it with a new one 4 years ago.

    2.-excessive lean air/fuel ratio... I did replace the air filter 2
    months before the test. I have used fuel injector and fuel system
    cleaners over this year

    3.-malfunctioning catalytic converter - 3-way catalyst only.... this is
    possible with the age of the car, but I would think that the HC and CO
    readings would be higher too? There is good exhaust out of my tailpipe,
    so the cat is not plugged. I did not measure the pipe pressure before
    and after the cat though.

    4.-excessive spark advance... I change the spark plugs myself, gap them
    properly at 0.040”, the current four are one year old, Champion brand
    RC12YC, traditional flat copper core. I do not use platinum or iridium

    5.-faulty thermostatic air cleaner system.... air filter is new, I did
    clean the throttle body valve this summer.

    6.-engine deposits or mechanical defect..... my engine runs and idles
    well. I do oil changes every 5000 - 7000 Km, mostly highway driving.
    This past summer I did do a mild engine flush using 1 L of ATF
    transmission fluid before an oil change. Folks have recommended this
    over concentrated flush chemicals, never had problems.

    7.-faulty cooling system... I did replace a failed water pump in
    September, coolant was flushed and replaced. I did replace my accessory
    belt. I also replaced a faulty temp sensor in July’08. The pigtail
    harness to this coolant temp sensor was corroded and caused running
    problems with my engine 2 weeks ago (stalling). I was stranded out of
    town when this happened and took the car to a shop where this pigtail
    harness was replaced. Engine was running fine thereafter and this 2008
    Emissions Test was performed at the same shop immediately after the repair.

    Any suggestions? .... Much appreciated.
    Thanks, Roger

    Three Emissions Tests results...
    Results: Nov 2008

    HC ppm @ 40Km/h ASM 2525, 23, limit 75, pass; @ Idle, 53, limit 200, pass

    CO % @ 40Km/h ASM 2525, 0.01, limit 0.42, pass; @ Idle, 0.00, limit 1, pass

    NO ppm @ 40Km/h ASM 2525, 1149, limit 576, FAIL; @ Idle, -, limit -, -
    (not done)

    @ 40Km/h RPM 1780, Dilution 14.41, valid
    @ Idle, RPM 745, Dilution 12.80, valid

    Analyzer Software Version: 4.54

    Results: 2006

    HC ppm @ 40Km/h ASM 2525, 7, limit 75, pass; @ Idle, 20, limit 200, pass

    CO % @ 40Km/h ASM 2525, 0.01, limit 0.42, pass; @ Idle, 0.16, limit 1, pass

    NO ppm @ 40Km/h ASM 2525, 550, limit 576, pass; @ Idle, -, limit -, -
    (not done)

    @ 40Km/h RPM 2858, Dilution 14.2, valid
    @ Idle, RPM 751, Dilution 12.6, valid

    Analyzer Software Version: 3.53

    Results: 2004

    HC ppm @ 40Km/h ASM 2525, 33, limit 86, pass; @ Idle, 196, limit 200, pass

    CO % @ 40Km/h ASM 2525, 0.02, limit 0.48, pass; @ Idle, 0.33, limit 1, pass

    NO ppm @ 40Km/h ASM 2525, 301, limit 663, pass; @ Idle, -, limit -, -
    (not done)

    @ 40Km/h RPM 1982, Dilution 14.9, valid
    @ Idle, RPM 760, Dilution 13.20, valid

    Analyzer Software Version: 3.16
    Roger E, Nov 25, 2008
  2. Roger E

    Bob Shuman Guest


    I have a few questions and a comment:

    Is the Service Engine Light lit? (You do not say...)
    Why do you think "the EGR valve is fine?"
    How many total miles on the engine/vehicle?
    How many miles in the 4+ years since the old EGR was replaced?
    When you replaced the EGR valve, did you also thoroughly clean the intake
    manifold port?

    Based on the symptoms you describe, I'd personally suspect the EGR is not
    operating correctly (if I recall correctly, the '95 was still vacuum
    operated so look at the rubber hose and diaphragm for small cracks) or the
    EGR passage in the manifold is partially blocked. By the way, 4 years and
    50K miles is about all you get from the EGR, especially if the engine burns
    a good deal of oil.

    Good luck.

    Bob Shuman, Nov 25, 2008
  3. Roger E

    Roger E Guest

    Hi Bob
    Thanks for your reply.

    No service light is not on.

    The original EGR valve gave me trouble back in 2004, not before then,
    and lasted for about 9 years. What happened then was my car was stalling
    when dropping the RPM on the engine, example decelerating and coming to
    a stop. I had removed that EGR valve and cleaned it with carb cleaner...
    the benefit lasted a couple of weeks then it began to stall again. I
    replaced the EGR in Oct 2004 and have not had the same trouble since then.

    Total mileage of my Saturn: 228,800 Km / 142,000 mil. (mostly highway)

    Total mileage of my Saturn since the old EGR was replaced: 81,700 Km /
    50,700 mil. (done @ 147,000 Km).

    I cleaned the base where the EGR valve mounts, the breather hose or
    crankcase vent hose, the throttle bore and plate, the hose to the PCV
    valve and replaced the PCV valve. I did not take apart the intake
    manifold. Do you mean to get at the gasket too? As I understand it, that
    is a big job..... here is a link to a doc as I understand that you mean
    by accessing this port. Am I right?

    http://wiki.rockauto.com/2000 SATURN SL SERIES 1.9L 116cid L4 FI (8)_Intake Manifold Gasket_0_0

    The vacuum hoses and PCV grommet are in good shape.

    Yes, this car does seem to burn alot of oil.... 1L every 2000 Km or so.

    I'll remove the EGR valve to examine it this weekend and clean it w/
    carb cleaner.... but it seems to be operating well at present.

    Thanks, Roger

    Roger E, Nov 28, 2008
  4. Roger E

    JimR Guest

    You've got to stop using Nitro while you are running it at the Funny Car
    Circuit :)

    Sorry I can't offer any real help. I just went out to check the
    emissions inspection reports on my 97 SL2, but for at least the last 4
    years, they have not listed actual readings (here in CT), only pass/fail.

    Good luck with yours.

    JimR, Nov 28, 2008
  5. Roger E

    navaidstech Guest

    Are you referring to a vacuum type EGR?
    Mine is 17 years old with 330k miles on it and still gives me good
    emission tests (except for the last one, it was a close pass - it
    might fail the next one in a couple of months)

    navaidstech, Nov 29, 2008
  6. Roger E

    Roger E Guest

    Hi Bob

    I removed my EGR valve on the weekend. There was a fair amount of carbon
    in it, however the valve spring was not sticking. I did clean out the
    valve holes and spring the best I could with carb cleaner/solvent. The
    car still runs ok. I'm going to replace the 20 month old RC12YC Champion
    spark plugs that are currently in the engine with RC14YC's, a spark plug
    with a higher heat range.

    I'm not sure if the problem is with the catalytic converter......
    exhaust is flowing, no plugs in the pipe, and CO and HC test results
    were always good. Maybe I should do another retest first, see if
    cleaning the EGR valve, changing the spark plugs, and using 91 octane
    gas works?

    Thanks, Roger
    Roger E, Dec 1, 2008
  7. Roger E

    Bob Shuman Guest


    It might be worth re-checking the NO emissions before you do any more work.
    The blocked passages could have been the root issue here. When you had the
    EGR out, did you also verify that the vacuum control was working properly
    (since failure in the diaphragm and/or the vacuum hose are common for that

    On the higher heat range plugs, I personally do not believe those are your
    problem. I would make sure they are clean and gapped properly though since
    the carbon you saw in the manifold from the oil consumption is likely also
    on those plugs too.

    On the high octane fuel, in my opinion this will not do anything to help you
    since that year Saturn did not use computer advanced timing to allow you to
    get any advantage from the higher octane. (If anything, it might even cause
    the vehicle to run worse. At best, all you are doing is paying more for the

    Good luck and let us know what you find is the problem.

    Bob Shuman, Dec 2, 2008
  8. Roger E

    Roger Guest

    Roger, Dec 3, 2008
  9. Roger E

    danielr Guest

    I hope this helps:
    I have a SL1, 1997, SOHC, 171000 KM.
    I ONLY use Synthetic oil Mobil 5W30 (good deal @ Costco), changed
    every 5000 Km. I ONLY use the K&N oil filter. I prefer to invest in
    preventive maintenance.
    Every couple of years (here in Toronto, Canada), I must have it
    emission test certified for at time of license renewal, which is the
    date of my birthday (February! Bloody Winter cool!).
    The tric I use (again, just my situation, which might apply to you or
    not), is to have the engine VERY hot before going to testsite, and
    change the PCV valve (regardless how good it mght look from outside),
    a couple of hours before.
    Also, I fill the tank with the highest octane gasoilne.
    Regulations here require the testing of leakage from the gas tank cup.
    I have another cup (brand new), which I ONLY use at test time, to swap
    few hours before the test.
    Somehow (yes; folks; I'm knocking wood), seems to have helped.
    Good luck.
    danielr, Dec 4, 2008
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