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Old 10-30-2013, 08:20 PM   #1
gregbenoit
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Default MY 07 STi won't pass smog…Please help!

My 2007 STi won't pass a smog check. I did mod my car but it has been back to stock for a couple of years now. I have no idea what it could be. Any help would be appreciated.

Thanks, Greg
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Old 10-30-2013, 08:50 PM   #2
JonnyV2889
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Quote:
Originally Posted by gregbenoit View Post
My 2007 STi won't pass a smog check. I did mod my car but it has been back to stock for a couple of years now. I have no idea what it could be. Any help would be appreciated.

Thanks, Greg
Very descriptive. Maybe if you provide more information about what was done previously, you might get a reasonable response. Did you not have to get smogged last year?
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Old 10-30-2013, 10:36 PM   #3
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I'm sorry. I posted this thread in a panicked rush. I had a catless exhaust system and a protune from Jon at HB Speed in Califonia. I changed the intake to a Cold air set-up. I also switched the fuel pump. A basic "Stage 2" set-up. After it was tuned it was boosting about 21psi. Then the motor blew. I put all the stock parts back on and I took the car to Subaru in Fullerton, Ca and they put a new short block in it. After I got it back it was bone stock and nothing has been changed since. This the first year that I've needed to smog my car.
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Old 10-30-2013, 11:30 PM   #4
kpluiten
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What did they fail you for? Codes? Emissions? Visual inspection?

Also, blowing you motor, returning to stock and defrauding SOA for a new motor. Weak.
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Old 10-31-2013, 12:01 AM   #5
gregbenoit
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Originally Posted by kpluiten View Post
What did they fail you for? Codes? Emissions? Visual inspection? Also, blowing you motor, returning to stock and defrauding SOA for a new motor. Weak.
Passed everything but emissions...It passed in higher rpms but it failed at idle. And I really DGAF what you think is weak. Any and all info is appreciated but comments/opinions are not necessary.
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Old 10-31-2013, 10:58 AM   #6
CRAZYHAWK
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Do you have a CEL?
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Old 10-31-2013, 12:02 PM   #7
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No CEL's. The car runs just as good as when I bought it. I did hear something about the valves tightening up and restricting emission flow. But I really don't know.
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Old 10-31-2013, 01:33 PM   #8
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Failed at idle would suggest bad 02 sensor, or bad catalyst. Both of which SHOULD turn on the CEL. In any case, you're probably going to have to take it to the dealer so they can use their diagnostic equipment to figure it out.
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Old 10-31-2013, 02:14 PM   #9
gregbenoit
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Originally Posted by Bacon117 View Post
Failed at idle would suggest bad 02 sensor, or bad catalyst. Both of which SHOULD turn on the CEL. In any case, you're probably going to have to take it to the dealer so they can use their diagnostic equipment to figure it out.
I took it to the dealer and they couldn't find anything wrong. They checked the o2 sensor and the cats too. I left the dealership with absolutley no answers.
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Old 10-31-2013, 02:22 PM   #10
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Dealer just shrugged and said GTFO? Interesting. Do you know specifically what the smog tester said failed? CO2, NOx, etc.?
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Old 10-31-2013, 02:40 PM   #11
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If you mean the valve adjustments are tighter than spec. , have them
readjusted. Tightening the valves would produce less power near idle,
and more at high rpm.

Quote:
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No CEL's. The car runs just as good as when I bought it. I did hear something about the valves tightening up and restricting emission flow. But I really don't know.
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Old 10-31-2013, 02:42 PM   #12
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Did you flash a stock tune back on the ECU after getting it running again? And when you say all stock...all stock exhaust parts including the cats?
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Old 10-31-2013, 03:08 PM   #13
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Originally Posted by Bacon117 View Post
Dealer just shrugged and said GTFO? Interesting. Do you know specifically what the smog tester said failed? CO2, NOx, etc.?
Pretty much. The service advisor kept my car for a week and then told me that the tech couldn't figure it out. I was super disappointed. I'm not sure what failed. I do have the paperwork. I'll check and post it.
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Old 10-31-2013, 03:10 PM   #14
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Did you flash a stock tune back on the ECU after getting it running again? And when you say all stock...all stock exhaust parts including the cats?
Yes and yes.
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Old 11-01-2013, 09:45 AM   #15
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It's probably a cylinder balance issue. One cylinder is running slightly lean, but another is running rich. Overall the engine is stoich, but emissions are bad. A lean cylinder will create NOx, while a rich will create CO. The catalyst should take care of the CO, but a gasoline engine doesn't do anything with NOx, because it isn't supposed to run lean. (As an interesting aside, that's what the new diesel fluid in modern diesel pickups is for, it removes NOx from the exhaust). This is why I was curios about what you actually failed. If you had High NOx, this would indicate one cylinder is running lean.

But, What's causing the cylinder imbalance is the question. It could be valve lash. You can also measure exhaust temperature at idle to see if there are any differences. You might also want to do a compression check just to see if there is any cylinder imbalances there.

Last edited by Bacon117; 11-01-2013 at 09:50 AM.
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Old 11-01-2013, 01:57 PM   #16
gregbenoit
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Quote:
Originally Posted by Bacon117 View Post
It's probably a cylinder balance issue. One cylinder is running slightly lean, but another is running rich. Overall the engine is stoich, but emissions are bad. A lean cylinder will create NOx, while a rich will create CO. The catalyst should take care of the CO, but a gasoline engine doesn't do anything with NOx, because it isn't supposed to run lean. (As an interesting aside, that's what the new diesel fluid in modern diesel pickups is for, it removes NOx from the exhaust). This is why I was curios about what you actually failed. If you had High NOx, this would indicate one cylinder is running lean.

But, What's causing the cylinder imbalance is the question. It could be valve lash. You can also measure exhaust temperature at idle to see if there are any differences. You might also want to do a compression check just to see if there is any cylinder imbalances there.
Thank you for the info.
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