1992 SHO CA Emission failure

Discussion in 'Engine, Intake, Exhaust and Drive Line' started by Greg Millard, Oct 15, 2019.

  1. Greg Millard

    Greg Millard New Member

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    The car runs fantastic and since I sleeved the EGR tube with 304L it even sounds great(no whisper leaks)
    My problem is I have trouble thinking a minor leak in the EGR tube would cause high NO readings - everything else passed but NO reading @ 15mph measured just over at 540 vs 537 (ppm) & measured 859 vs a max allowed 494. @25 mph.

    I am open to any & all alternatives wires, plugs, dist cap MAF sensor, O2 sensor but I will first have it rechecked with the leak nowremedied, then move on.

    Any rec on brand of plugs/wires to use

    One individual suggest I pull the SPOUT and retest - perhaps a last resort but I'd prefer to make it right.

    Any ,& all comments appreciated, Retrogreg
     
  2. luigisho

    luigisho SHO Member

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    SPOUT was my first idea. Really my only idea.

    How many miles?

    Your car may or may not have been built to pass current emission standards. Also higher mileage cars with carbon buildup tend to have increased NOx. You can get new factory grade catalytic converters and pay through the nose plus install. You can chase your backside trying to pass smog on an older vehicle in Cali. I hope you find a better answer than SPOUT but that is what I would try first. Report back!

    try this for ideas. https://www.eng-tips.com/viewthread.cfm?qid=44564
     
  3. rubydist

    rubydist SHO Master Staff Member Super Moderators

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    That thread is right on - my experience is that just slightly lean can make NOx go up rapidly. That would be my first place of checking - a dirty mafs that doesn't read all the air, or old oxy sensors that are telling the pcm to run leaner than it should, or a little vacuum leak on the intake.

    If you chase that to ground with no success, then I would be looking at the timing. Is the crank damper spun a little so that the timing is too advanced?

    Those are the most likely candidates in my experience.
     
  4. Greg Millard

    Greg Millard New Member

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    Thanks - just got off the phone with a very knowledgeable guy who will have a look at my SHO and offer an opinion - I will report back, thks again, Greg
     
  5. Greg Millard

    Greg Millard New Member

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    IMG_20191016_125835.jpg up in
    Good Call on the 'cats' ....it seems the ones o n the car were of the much smaller " high-flow 49 state type" that is being rectified - see pic - will update with results of emisions cert testing.
     
  6. Greg Millard

    Greg Millard New Member

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    Ok new CA certified cats installed - will drive for a few days then re-test - here is a pics of new larger cats installed, Greg IMG_20191016_143237.jpg
     
  7. luigisho

    luigisho SHO Member

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    I wish you well with the fresh cats. Post back with results. Hopefully the extra material does the trick.

    That oil pan and tranny look way too clean to be a SHO. Usually a good coating of -whatever's leaking this time- makes it a little grimy. That thing is crazy clean under there.
     
  8. sperold

    sperold Last to Know Supporting Member

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    Keep the old ones, you can actually sell them to re-cycler and scrap dealers.
     

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