Hi, I finally passed the bi-annual California Smog Test. Thanks to all who provided suggestions and inputs. As a recap, I failed initially for high CO but passed HC and NOx. The data is in the table below. (If it doesn't come out in email, I will resend in simper text form).
The tell-tale indicator was that O2 level was at 0%, indicating there was no more oxygen left to convert CO to CO2. I found a useful article from Toyota with a graph showing the relationship between CO2, HC, NOx and CO vs air fuel ratio - www.autoshop101.com/forms/h56.pdf The oxygen sensor was new and putting out a variable voltage. So high CO indicated a rich mixture and could be explained by 1) leaking fuel injectors, 2) bad temp sensor causing ECU to run rich or 3) Air Flow Meter out of adjustment. The temp sensor was OK (using Handsome Eric's L-Jet Tune Up procedures at http://www.hiperformancestore.com/Ljetspider.htm ). I opted to go after the spring setting on the AFM rather than pull and check the injectors. By going 7 notches tighter (leaner), I went overboard and FAILED for high NOx (Table below) the second time. I backed off to 3 notches tighter (leaner) and PASSED, barely on the third time. I was bumping up close to max HC at 15mph and max CO at 25mph. I could probably go one more notch leaner, but NOx is dangerously high at 15mph. Here are the results (not sure if this will print properly): DATE 2/5/2011 2/23/2011 2/28/2011 ODO 222151 222597 222608 Note Standard AFM setting 7 notches lean 3 notches lean *15mph Test* ** *FAIL* *FAIL* * PASS* ** RPM 2801 @15mph 2834 @15mph 2829 @ 15mph <2829@%2015mph> HC(PPM) max allowable 124 124 124 avg for passing vehicles 31 31 31 *HC actual* *95* * 43* *122* ** CO (%) max allowable 0.78% 0.78% 0.78% avg for passing vehicles 0.10% 0.10% 0.10% *CO actual* *0.78%* *0.05%* *0.69%* ** ** CO2 (%) *CO2 actual* *14.50%* *15.00%* *14.60%* ** ** O2 (%) *O2 actual* *0.00%* *0.10%* *0.20%* ** NO(PPM) max allowable 815 815 815 avg for passing vehicles 237 237 237 *NO actual* *477* *1599* *729* ** ** ** ** ** ** *25mph Test* ** *FAIL* *FAIL* *PASS* ** RPM 2870 @25mph 2853 @ 25mph 2847 @ 25mph <2847@25mph> HC(PPM) max allowable 98 98 98 avg for passing vehicles 20 20 20 *HC actual* *48* *33* *65* ** CO (%) max allowable 0.66% 0.66% 0.66% avg for passing vehicles 0.09% 0.09% 0.09% *CO actual* *0.78%* 0.05% 0.66% CO2 (%) *CO2 actual* *14.50%* *15.00%* *14.70%* ** ** O2 (%) *O2 actual* *0.00%* *0.10%* *0.00%* ** NO(PPM) max allowable 754 754 754 avg for passing vehicles 199 199 199 *NO actual* *274* *1424* *287* Two final notes: 1) In theory, the ECU should be able to make the correct air fuel adjustments with input from the O2 sensor. But in reality, it appears that the AFM signal sets the fuel metering and the ECU does fine tuning around the O2 sensor output. If the AFM is too far off, then the fine tuning won't be within range. Hence, adjustments to the AFM spring are required on an AFM that has over 200K miles racked up. 2) The smog tech knows to pre-heat the catalytic convertor prior to starting the test. And the two tests were run in 1st and 2nd gear to keep the RPMs high and the cat hot. So it looks like my cat is nearing the end of its life. Cheers, Charlie '89 Spider -- to be removed from alfa, see http://www.digest.net/bin/digest-subs.cgi or email "unsubscribe alfa" to [email protected]
