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Registered
Join Date: Aug 2004
Location: Ottawa
Posts: 366
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Strange emission test failure No ppm
My 944s2 failed the emission test at 40 Km/h 1928 Rpm.
HC ppm Limit 62 Reading 2 Pass CO% Limit 0.35 Reading 0.00 Pass NO ppm Limit 0700 Reading 863 FAIL Any thoughts why it would fail The NO PPM ?
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Doug 97 C2S 993(last one) 95 993 cab- 85 911 M491 87 944 Turbo- 70 914-6 63 911 |
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04-23-2008, 06:43 AM
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In the Fires of Hell.....
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NOx is usually a CAT issue.
Try to find a stock one here or some other forum, or you will be paying $$$$$$ Cheers, Keith
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PCA Instructor: '88 951S - with LBE, Guru chips, 3Bar FPR, 1.3mm shimmed WG, 3120 lbs, 256 RWHP, 15 psig boost |
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04-23-2008, 08:56 AM
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Registered
Join Date: May 2004
Location: Franklin, MA
Posts: 49
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Once I failed because the tech selected 8 cyl, not 4 cyl. which skewed the results.
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04-23-2008, 09:40 AM
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Registered
Join Date: Aug 2004
Location: Ottawa
Posts: 366
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Quote:
Is there any truth to taking the car for a good long drive so that the cat is very hot before you get the emission test?
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Doug 97 C2S 993(last one) 95 993 cab- 85 911 M491 87 944 Turbo- 70 914-6 63 911 |
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04-23-2008, 09:52 AM
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Trying to work for parts!
Join Date: Oct 2006
Location: MO
Posts: 1,760
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yes there is. i would do that before doing the cat.
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86 Metallic Grey 85.5 Metallic graphite - Gone |
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04-23-2008, 10:46 AM
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winter-hater club member
Join Date: Oct 2003
Location: salt lake city, utah
Posts: 24,705
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vacuum leak will cause high NOx problems. mine passed, but just barely, until i replaced ALL the vacuum lines, including the stuff under the intake manifold. after, it passed with a lot of room to spare, which makes me wish i had saved the cat i had that had been gutted....
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2000 Corvette - ????, 2007 Buell XB9R - Astrid, 1996 Discovery - Piglet, 2000 Forester "COOL PRIUS!" - Nobody Ever |
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04-23-2008, 11:35 AM
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Join Date: Apr 2008
Posts: 35
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With low CO & HC, but high NOx, you're engine is definitely running too lean.
Before assuming the cat's bad, I'd check the easy stuff first. As mentioned before, check for vacuum leaks e.g., broken/cracked/disconnected vacuum lines. Check O2 sensor, but a failure there usually results in overly rich mix, but it's easy to check (see procedure at Clarks Garage.) Check proper operation of throttle position switch, also detailed at Clark's. Check that someone didn't monkey with the air bypass screw. It's the one that's supposed to have a metal plug on top so that it's not played with. If the metal plug is in, it's probably ok. If not, adjust it to a more rich mixture. If you don't have a gas analyzer, as most of us don't, it'll be trial and error. Also detailed at Clarks. |
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04-24-2008, 05:29 AM
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944 Turbo
