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Forum > Failed Smog Test > Question

1995 Nissan Sentra failed smog check for high HC. What could be the problem?

HC for both 15 and 25 mph were at the limit (92 and 57 respectively) failed smog bec. timing was at 0 tdc. retested adjusting timing to 8 btdc. fail HC by 2 on the 25 mph. 15 mph was at the limit. spark plug,wires,rotor replaced. what could be the problem? would adjusting timing help? how much adjustment is acceptable for DMV? thank you.
Answer:

Timing may very well be the problem however you really should have it set where the manafacturer recommends it. The state will allow you 3 degrees +/-. Any more than that and your Sentra will fail the funtional timing portion of the inspection. Other problems to look for would be compression, defective catalytic converter, and perhaps incorrect air/fuel mixture due to worn oxygen sensor. posted by SmogTips Support

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