Hey guys, my daily driver Miata failed its smog test this morning as a gross polluter, even though it's completely stock with only 140,000 miles on the clock. I bought it a year ago, at which time the original owner smogged it without issue, and since then I've changed the spark plugs, air filter and timing belt. My numbers for CO are fine, but HC at 15 mph is high and NO is off the charts at both 15 and 25 mph.

I'm new to the Sac area, but what are my options as far as repair? Can anyone suggest a good shop that will charge me a fair amount and actually know what needs to be done to make it pass smog?

Thanks,
Andrew

 

Sounds like you need a cat

 

Think that will do it? I get one free retest, so let me know if there's anything else I can do before getting retested.

 

yea try the cat..if its stock..im thinkin that is something that happens a lot.

 

Cool, I'll find a muffler shop this weekend and try that.

I wish these morons at smog stations would be a little more helpful in providing advice as to why your car failed. Useless turds... i-Club on the other hand: uber helpful. Thanks, guys, I'll let you know how it turns out.

 

Get a new cat, run some injector cleaner through, get a clean tank of gas before you go and make sure you drive your car a while & its extra hot before you take it in, the hotter the cat is the cleaner it will come out.

 

Made an appointment for a new cat to be installed on Monday. Will get some injector cleaner today and start that in on my fresh tank of gas this weekend. Will top off with 92 octane before my retest and will heat the crap out of everything beforehand. Thanks again!

 

Definitely don't run 92. Just get regular from Chevron or Texaco (same place basically) and you should be good to go.

 

Oh, ok. Any particular reason that it's better to run 87 for a smog check? Is 91 too rich?

 

Gas with a higher octane (knock resistance) is less likely to ignite prematurely........in a motor that doesn't need it, it's less likely to combust completely, which means your HC count will be through the roof. Hydrocarbons = oil and gas. Either getting through the combusion chamber means more particulates, and that's one of the reason's you're running so high.

 

Alright, that makes sense. Thanks for that insight into the HC portion of it.

What's the cause of the NO being so high? Anything I can do for that beyond those methods already discussed (new cat, injector cleaner, new gas and hot engine)?