LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

Failed emissions, what do I need to fix?

Old Jan 4, 2005 | 02:07 PM
  #1  
rlax31's Avatar
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Failed emissions, what do I need to fix?

I failed the emissions test today. It failed at 15mph, but passed at 25mph. The guy at the station said that it could be one of two things: The cat, or the EGR.

Performance mods are as follows:
GMMG cat-back, A4-M6 swap, SLP intake, SFC's, 4.10 gears, throttle body bypass.

What do you think is wrong? Most likely a malfunctioning EGR valve? cat going bad? Both have never been touched since I've had the car.
Old Jan 4, 2005 | 02:29 PM
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Re: Failed emissions, what do I need to fix?

I think a bad EGR would throw a code, do you have any codes showing?
Old Jan 4, 2005 | 06:11 PM
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Re: Failed emissions, what do I need to fix?

No codes
Old Jan 4, 2005 | 07:33 PM
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Re: Failed emissions, what do I need to fix?

Doesn't have to show a code, how many miles?
Old Jan 4, 2005 | 07:40 PM
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Re: Failed emissions, what do I need to fix?

57k
Old Jan 4, 2005 | 07:53 PM
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Re: Failed emissions, what do I need to fix?

How bad did you fail? make sure its good and warmed up and throw some revs before you go in there, clear all the crap out, or hold a high idle for a little bit before you go through. you can also run some of the "Guarenteed to pass" crap, or put some holes in your exhaust after the 02s but not too close to the tips (so they cant see/hear them)
Old Jan 4, 2005 | 09:13 PM
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Re: Failed emissions, what do I need to fix?

at 15mph the NO ppm limit is 586, and I read 685

at 25 the limit is 531, I read 334
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