1976 Chevrolet Truck wont pass smog

WHYTEKNITE61

MEMBER
1976 CHEVROLET TRUCK

The NOX gases too high replaced carb rechecked vacuum lines and reconnected them corectly removed egr valve cleaned execes carbon replaced gasket checked and adjusted engine timeing I need some direction or answers to relive this problem

Sunday, September 29th, 2013 AT 2:55 AM

3 Replies

HMAC300

MECHANIC
48,601 POSTS

Change oil and filter first then drive about 20 miles on eway and get retested then it will probably pass

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Sunday, September 29th, 2013 AT 6:31 AM

WHYTEKNITE61

MEMBER
2 POSTS

Just wondering but how did you come up with that answer im not questioning your abilities becaues ive seen and heard stranger things working and there is no greater knowlege then experience I know that in 40yrs you have seen things myself as a retired brake and front end tec there are a few fixes I cant explaine thank you

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Sunday, September 29th, 2013 AT 9:14 PM

HMAC300

MECHANIC
48,601 POSTS

Because most of the time, vehicles aren't properly warmed up and oilnot changed for ages so gas build up and it makes hc & nox high. Because your vehicle is a 76 it's not as stringent as the newer cars. So if you change the oil and filter you get a lot of fuel that has built up out of the engine and by driving about 15-20 miles on eway helps it further then getting it tested right away the engine is properly warmed up. Of course it could be something else as well but normally these pass with flying colors.

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Monday, September 30th, 2013 AT 6:44 AM