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Old 08-11-2003, 09:42 AM
inspector1
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Gas additives are worthless for 'improving' emissions test results, even if a vehicle is in fuel control; they may increase HC readings.

if when you retest the NOx is still high, check the temp sensors for accurate function, timing, and cat.

If HC and/or CO readings are marginal passes, check O2 for slow switching.
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