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Old 05-23-2020, 10:58 AM   #1
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Failed CA smog - High NOx

Hi Everyone,
Returning after several years as we just purchased another Boxster (1999). However, trying to get it registered and getting it smog tested it did not pass due to high NOx. I bought a bottle of Lucas gas additive that indicated on the bottle that it reduces NOx emissions. Can anyone recommend anything else I can do to pass the test or is it something else? The car has 84K miles and the check engine light has NOT come on. Thanks in advance for your replies and assistance.
Kevin

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Old 05-23-2020, 11:30 AM   #2
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My first question is, does the CEL light come on when you first turn on the ignition? Sellers have been known to disable, also in California the seller is responsible for smog.

That being said, I'd check with a scanner for codes. High N0x is caused by high combustion temperature. This can be from lean mixtures or advanced ignition timing.

Causes could be MAF, injectors or fuel delivery, air leaks or 02 sensors. Might pull a few plugs and look at color.

Good Luck
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Old 05-23-2020, 11:39 AM   #3
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The CEL does come on when the key is turned and I kinda blew it on the seller getting it smogged...not sure if I have any recourse. A key learning experience.

I am in the process of finding someone with a scanner other than the dealer.

I'm hoping the gas additive will help and will do your recommended advice. Thanks.
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Old 05-23-2020, 11:52 AM   #4
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How old is the gas in the tank? There is no EGR on these cars so the three way cat convertors have to perform. If possible I'd do the racer tune by getting car up to temps then high rpms to heat up and clear cats. Did you get car well up to temp on freeway to ensure cats were well lit before taking to smog?

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Old 05-23-2020, 12:02 PM   #5
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I'm not sure of the gas but I just filled it up (when I added the Lucas gas additive) with Chevron supreme. I will do the freeway trip before I take it in again. I am hoping to do the smog again on Monday or Tuesday to give the additive to do whatever its going to do. Thanks again Monty.
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Old 05-28-2020, 10:53 AM   #6
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First of all Monty....Thank you SO much for your technical advice. It seemed to help as the car passed smog this morning!! Thank you again
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Old 05-28-2020, 01:06 PM   #7
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Great News! Glad to help.

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