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Registered
Join Date: Sep 2003
Location: Milwaukee, WI
Posts: 121
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Emissions / Smog Question - High HC under decel
My car failed WI emissions, it's a 78 SC. I got the car in August and have put about 1500 miles on it. It has used less than 1/2 qt oil in this time. Car doesn't smoke at all, doesn't drip. I don't have leakdown and compression #s
 Overall the test results were ok with the exception of HC levels under deceleration, which were very high. WI emissions are tested by putting the car on rollers and running at various speeds, idle, accel, decel while the gases are measured. The 1st output report breaks down the levels for the conditions. Below are the reports that the test station gave me. Would anyone car to give their thoughts on where the problem might be? For my car, the limits are HC 3.000, CO 65.000, NOx 5.000. HC is the only part that my car failed on. The 1st report below compares to a reference (new) car which makes it look like my NOx is too high, but actually it is ok.   Any help would be greatly appreciated. Best Regards, Daryl Milw, WI |
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10-12-2006, 09:51 AM
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Join Date: Jan 2002
Location: Long Beach CA, the sewer by the sea.
Posts: 37,748
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Those are some tough standards. Do you really have that much smog? Anyway, not being an expert, see that the decel valve, or whatever CIS has for that feature, is working. I'm not sure why engines must wind down slowly, but that's how the smog system is designed. On the old MFI systems, if the gas was let off, a switch cut off the fuel flow. To me, that would keep emmisions low to none. I guess I don't know much, because they don't let it work that way now.
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10-12-2006, 11:12 AM
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Join Date: Sep 2003
Location: Milwaukee, WI
Posts: 121
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Thanks
The units are grams/mile. I think in CA they use PPM - so the limits you'd probably see are a little different. I've never had trouble with a car passing before, so generally they're ok I think. My car is eligible for collector plates, but I've gotta pass the emissions test 1x as a requirement for the plates. Then no emissions testing - ever! Last edited by IlMostro; 10-13-2006 at 05:23 AM.. |
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10-12-2006, 11:41 AM
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Registered
Join Date: Sep 2003
Location: Milwaukee, WI
Posts: 121
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Everyone must be busy reading the 165mph targa thread.
Did I mention that the high HC under deceleration is when I'm slowing down from a 10k rpm, 180mph run in my "correct" engined SC?  Anyone . . . . . . anyone . . . . . . . |
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10-13-2006, 05:19 AM
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Join Date: Sep 2003
Location: Milwaukee, WI
Posts: 121
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. . .
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10-14-2006, 06:11 AM
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Registered
Join Date: Oct 2003
Location: London Ont Canada
Posts: 3,120
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The decel valve was present on the SC to keep the throttle open slightly (allowing more air to reduce HC on decel. If its,s not hooked up then reconect it.It was often unhooked because it caused an annoying high engine speed on decel and or a jerk when it reached idle.If it is broken or missing you could try setting your idle speed up to about 1300/1400 rpm and adjusting mixture lean(3mm hex key at contol flap) and try the test again.
__________________
1980 911 SC 3.6 coupe sold 1995 993 coupe 1966 Mustang Shelby clone 1964 Corvair Spyder Turbo gone 2012 Boss 302 |
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10-14-2006, 11:29 AM
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Registered
Join Date: Mar 2001
Location: SF Bay, California
Posts: 176
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Smog
Is your smog pump working? I failed once on my 79 to figure out that the vacuum hose that opens the smog air pump valve was eaten through and doing nothing. Once I replaced the hose and tuned the mixture with a gunson gas tester, it passed with flying colors. Of course I readjusted my mixture back to 3.5% (John Walker's recommendation) after the test.
Just some ideas for you. GB |
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10-14-2006, 11:35 AM
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Registered
Join Date: Sep 2003
Location: Milwaukee, WI
Posts: 121
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Johns and GB
Thanks for the tips, I'll check both! Best Regards, Daryl |
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10-14-2006, 01:27 PM
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