Re; Another Emissions Question...Again

[Fred Sacks <fredsacks@domain.elided>]

Charles--

Thanks for the input.

Checking compression is a good idea, and it's easy enough to do. 
Given the high numbers though for NOx, CO & CO2, and the slightly 
carboned plugs, and also the fact the car performs well, I'm starting 
to think that it might be the Oxygen Sensor.  I haven't checked the 
manual yet for spec voltage through the sensor(if it's in there), but 
that is also part of the next diagnosis.

Any other thoughts out there???

Fred Sacks
89 Graduate

At 12:03 AM -0400 9/30/01, alfa-digest wrote:
>Hi Fred,
>	California Smog Test does not monitor NOx.  Just HC and CO. 
>My '89 Spider
>flunked big time because I had a burned exhaust valve.  I didn't notice a
>performance difference, but it showed up on a compression test.  Here are my
>results BEFORE and AFTER a valve job. 
>
>						BEFORE	AFTER
>RPM						2330	2461
>HC(PPM)	max allowable				140	140
>	avg for passing vehicles		20	20
>	actual					222	10
>CO (%)	max allowable				1.00%	1.00%
>	avg for passing vehicles		0.10%	0.10%
>	actual					6.03%	0.08%
>CO2 (%)	max allowable				NA	NA
>	avg for passing vehicles		NA	NA
>	actual					9.90%	13.50%
>O2 (%)	max allowable				NA	NA
>	avg for passing vehicles		NA	NA
>	actual					1.90%	2.20%
>
>
>Your numbers:
>
>Item	Maximum		One month ago		Yesterday	Result
>
>NOx	1438		2245			1871		FAIL
>HC	187		229			186		Pass
>CO	1.05		.67			.69		Pass
>CO2	n/a		12.4			11.8		n/a
>O2	n/a		2.1			3.4		n/a
>
>	There not quite the same, but a properly running fuel 
>injected engine should
>pass the HC and CO numbers with a big margin.  Your numbers on HC and CO are
>really marginal.  The high NOx has me puzzled because it typically means an
>overly lean running engine.  But I don't know what happens when unburned gas
>get into the catalytic converter.  Maybe Eric could tell us.
>	At this point, I would ignore the NOx.  Do a compression 
>test.  If there is >
>20 lb variation from cylinder to cylinder, you might be looking at the start
>of a burned valve.  For your low mileage, I would doubt rings would cause
>compression variation if you do see it.
>
>Good Luck,
>Charlie S
>'89 Spider

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