Smog Adivce Needed

Discussion in 'California 2nd Genners' started by SG71SS, Nov 8, 2017.

  1. SG71SS

    SG71SS Veteran Member

    Every two years in December is the dreaded smog check for my 79 T/A with bone stock 403. Bleh..

    Long story short, two years ago failed miserably as gross polluter. Hydro carbons sky high and various vacuum lines missing:
    smog2015x.jpg

    Took her home and found numerous vacuum leaks, reconnected lines to vapor canister and carb, set timing, and fine tuned carb best I could and barely failed second time. HC a hair above max allowed. Notice NO right at the average:
    smog2015ax.jpg

    Decided to replace the catalytic converter and HC dropped big time but noticed NO went way up from 455 to 745:
    smog2015bx.jpg

    Question - Although I passed (yay!), what caused NO to shoot up after installing a brand new cat which helped HC drop way down?

    Thanks in advance! Wish me luck.
     
  2. Knuckle Dragger

    Knuckle Dragger Moderator Staff Member Lifetime Gold Member

    12,837
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    Nov 2, 2002
    Waddell AZ
    IMO, the converter is covering up a bit of a misfire and getting hot. In the middle picture you had high O2 and high HC which leads me to believe it's a misfire since the CO was good. Your O2 dropped but you CO2 didn't come up much in the last picture as I would have expected if the old cat was "bad". It could just be they didn't warm the converter up enough before the test too.

    Keep in mind it's been 10+ years since I had to diagnose a failure too :)
     
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  3. SG71SS

    SG71SS Veteran Member

    Thanks Dave! Very much appreciated.

    Since I just received my registration notice and have to take it in for smog test, any tips on where should I check for misfire? Last time I got the car running very smooth but my shade tree mechanic skills go only so far. :D
     
  4. Knuckle Dragger

    Knuckle Dragger Moderator Staff Member Lifetime Gold Member

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    Nov 2, 2002
    Waddell AZ
    How long ago was that passing test? IMO you're going to need a baseline to go from if that was last years test. You don't want to gross pollute again but if you have them do the pretest and it passes you're out double the fee. When I was doing the tests I might have over run the dyno MPH once or twice to blow a car out of the test if I thought it would fail and I knew the customer, well but most guys won't.

    If it was me and the car is ruining well, I'd drive it a bunch for a few days and take it in. Make sure it doesn't sit for a while before the guy gets to running the test and that you have 30 minutes or so driving before you show up so the cart is warm. The guy testing it wants to wham bam them in and out quickly and sometimes runs them too cold.

    Everyone I would know is way south of you. I have a friend at a Ford dealer in Riverside, and KDracer is out of the Temecula area IIRC. Both guys are honest testers with great knowledge. Batman (Jason) has a guy he uses but that's also going to be south of you in the Irvine area.
     
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  5. ol' grouch

    ol' grouch Veteran Member

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    Evansville, In.
    That's one advantage of living in S.W. Indiana. No smog tests at all.
     
  6. Knuckle Dragger

    Knuckle Dragger Moderator Staff Member Lifetime Gold Member

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    Waddell AZ
    I'm sure that is extremely helpful insight for SG71ss. Thanks for the informative helpful post :screwup:
     
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  7. SG71SS

    SG71SS Veteran Member

    Last time it took three tries to pass and the bottom test was the most recent which was about 1 1/2 years ago. I've driven the car maybe 500 miles since that last test and the car still runs great so I will use it as my baseline. I'll follow your advice and the cat nice and hot.
    Will report back with the results. Thanks again for your help Dave!
     
  8. MIDNIGHTBLUE

    MIDNIGHTBLUE Veteran Member

    1,861
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    Jul 28, 2000
    Hemet, CA
    I am wondering if any of the gasoline additives would help? I just ran my 97 Lincoln thru, used a can of the "Guaranteed to pass," with a tank of it and the tech told me, she had never had a car from this year pass as clean as mine. As a caveat, this is the first test I have ever had done and have no history or previous baseline.
    https://www.amazon.com/CRC-05063-Gu...UTF8&qid=1510681197&sr=1-1&keywords=pass+smog
     
  9. Knuckle Dragger

    Knuckle Dragger Moderator Staff Member Lifetime Gold Member

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    Nov 2, 2002
    Waddell AZ
    My fingers are crossed for you. Please post up with results when you get it done.
     

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