hey what's up guys, I need some help...my 1978 HONDA CVCC just recently failed the smog test pretty bad. I smog the car a few months ago and it passed but I tried again and no good. Here's my smog paper. The circle area is the the part I failed, everything else passed. Any kind of help on what is causing the car to fail would be much appreciated. Thanks!


By slayersluck at 2009-03-05

 

NOx is caused by high combustion temps.

If your car has an EGR, check it's operation. A failed EGR raises NOx.
Check your timing. Too far advanced, NOx goes up. Retard it 1* if it is correct (still within passing range).
The cat failing can cause higher NOx readings. I would assume your HC readings would be higher if it was failing, but only the 1st phase of the cat handles NOx and that could be the only part failing.

Lastly, dump a bottle of ISO Heet into a half tank of gas and resmog it. Should lower NOx some.

For the future, if you want to avouid having failed smog test results haunt the car (and they can), ask for a "pre-test" instead of a smog test. The only difference is the results of the pre-test aren't recorded and sent to the DMV. If it passes the pre-test, have them immediately do the actual test. If it fails, no harm done.

 

the car is running lean. you have carb problems. unfortunately on those old turds there are very few people that want to work on those carbs.