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

Failed Emissions with high NOX

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Old 11-03-2007, 05:14 PM
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Failed Emissions with high NOX

Maximums allowed: HC: 0.80 CO: 12.00 NOX: 2.00

1st Test: HC: 0.68 CO: 6.34 NOX: 2.30

After the first test failing due to high NOX i removed the Hypertech tuning and ran it through again.

Retest results: HC: .63 CO: 5.82 NOX: 2.02

Almost passed on the retry but still high NOX.

Any suggestions? The guy a the testing center says its most likey NOT the Cat, or else the other numbers would likely be higher as well.
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Old 11-03-2007, 05:21 PM
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EGR valve still on the engine?

high NoX is usually from a failed EGR system
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Old 11-03-2007, 06:15 PM
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Originally Posted by Dave89IROC
EGR valve still on the engine?

high NoX is usually from a failed EGR system
Yup - might be pluged up with carbon.

Otherwise is it running hot? Too much timing (but you set it to stock anyway), bad cat, possibly carboned up pistons and combustion chambers. Make sure to use premium gasoline - that will help too.
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