Topic: CA Smog Troubles
in Forum: C4 General Discussion
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San Jose, CA - USA
Joined: 5/10/2012
Posts: 81
Vette(s): 1988 Corvette / Blue Pearl
Hydrocarbon (HC) & Carbon Monoxides (CO) are the reasons I barely failed the CA Smog ( Emissions ) test the HC's were about 18% higher @ 15MPH & 19% @ 25 MPH . How can I lower these ? The Smog tech told me it shouldn't take much to get it right maybe a oil change and retard the timing no more then 3 deg. Has anyone else had this issue?
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Ahhh. Failed The Room of Doom in California, eh?
Post your numbers and the limits. HC and CO for what might be wrong, and O2 and CO help determine converter health. Also your Corvette's year would help.
Slightly elevated HC and CO usually indicate an ineffective catalyst. High HC by itself is a misfire. High CO is running rich, and will also be accompanied by high HC.
Google "5-gas emissions analyzer readings" to furthur your understanding of emissions test results. Here's the one I'll study later to re-fresh. http://www.autoshop101.com/forms/h56.pdf
Post your numbers and the limits. HC and CO for what might be wrong, and O2 and CO help determine converter health. Also your Corvette's year would help.
Slightly elevated HC and CO usually indicate an ineffective catalyst. High HC by itself is a misfire. High CO is running rich, and will also be accompanied by high HC.
Google "5-gas emissions analyzer readings" to furthur your understanding of emissions test results. Here's the one I'll study later to re-fresh. http://www.autoshop101.com/forms/h56.pdf
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San Jose, CA - USA
Joined: 5/10/2012
Posts: 81
Vette(s): 1988 Corvette / Blue Pearl
I'll Post the results soon, I retest tomorrow ,I changed the Oil , Knocked the Timing down 2 Deg. from 6 DEG. to 4 DEG. ( Car seems to like 4 DEG. Better ) no more pinging , I'd just realized it had been 1-1/2 years since my last Oil Change 
Shame on me for not keeping up with that ...too many cars & not enough memory on my part . I will get those numbers up soon.
Fail twice, and you're a "Gross Polluter". I'm not sure what it takes to pass after you receive this distinction, as I have never had one of my personal cars fail a smog inspection (seriously) in the 40+ years I've lived in SoCal. I was a Cali liscensed smog tech for about 10 years, and carried an ASE Master Auto Tech cert for 30 years. I know quite a bit about emissions, testing, and systems interactions. I was asking for your test numbers to see if I could help you zero-in on the actual problem, and increase your chances of passing the Room of Doom on the next test. Not out of curiosity. Oil changes aren't likely to help much, and the timing should be set to the spec on the under hood sticker, as the technician is supposed to verify the setting.
Good Luck
Good Luck
You may want to consider a pre-inspection in order to avoid the Gross Polluter designation. If it turns out your car isn't going to pass, the pre-inspection results won't count against you. Then, you can use the help here on the forum, along with help from your repair shop, to get the car passable. Take the "real" test when you know you're passable, and you can avoid Gross Polluter status.
|UPDATED|7/31/2013 8:44:46 AM (AZT)|/UPDATED|
Below is a little information from California's Bureau of Automotive Repair Website. You can read the whole page at
Q: What is a "pre-inspection" and how do I get one?
A: Motorists who believe their vehicles may not pass initial smog certification at local Smog Check stations may request that an inspection be conducted before an official smog certification test. This procedure can help vehicle owners avoid their vehicles being designated as "Gross Polluters," requiring final inspection at a Test-Only Center or a Gold Shield station. Smog Check stations may charge for this service only if authorized by the consumer; BAR does not regulate those charges and receives none of the proceeds.
|UPDATED|7/31/2013 8:44:46 AM (AZT)|/UPDATED|
~Laurie~
1985 and 1995 coupes:
I had a gross polluter once. Had to go to a "Gold Shield" certified station to clear the name. Same price but wondering why it was special. It only passed after doing a valve job. One exhaust valve not sealing and burnt. Good 'ole Ford inline six.
If it isn't broke, I haven't fixed it yet....
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San Jose, CA - USA
Joined: 5/10/2012
Posts: 81
Vette(s): 1988 Corvette / Blue Pearl
Here are those numbers @ 15 MPH (CA -Max) is 78 ppm / mine was @ 96 ppm
@ 25 MPH ( Ca-Max ) 86 ppm / Mine was @ 115 these are for the Hydrocarbons ( HC )
(CO) are as follows CA-Max is @ 15 MPH 0.51% / Mine was @ 0.36%
@ 25 MPH CA-Max is 0.42% / Mine is @ 0.43% ( CO)
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San Jose, CA - USA
Joined: 5/10/2012
Posts: 81
Vette(s): 1988 Corvette / Blue Pearl
Now as far the ( HC ) , Used motor oil carries a very high number of Hydrocarbons , I've hauled it , cleaned it , & refined it . Too much timing can also raise HC #'s , A dirty air filter can also . And the list goes on My father in law worked for GM and has worked on many C4's . Even though the factory setting is @ 6 deg. he said most C4's are happy @ 4 deg. From what the smog tech told me it shouldn't take much because those are not high numbers and should be easy fixes .I also checked the CA ( State ) web site for more info , They echoed the same, dirty oil, air filter & timing being too high could very well be the case . We shall soon see , I'd like to thank every last one of you with your great input & info .....I hope I can return the favor 1 day
|UPDATED|7/31/2013 5:11:24 PM (AZT)|/UPDATED|
|UPDATED|7/31/2013 5:11:24 PM (AZT)|/UPDATED|
I live in east Kern county and we don't have the dyno test. We just do idle and 2500 rpm check. My last test revealed HC was 30% of allowed and CO was 40% of allowed.
If I were to move north 10 miles I'd be in Inyo county were bi-annual smog testing is not required. There are 9 counties in Ca. were regular testing isn't required because of altitude. But testing is required to sell a car.
If it isn't broke, I haven't fixed it yet....
in Forum: C4 General Discussion
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