Failed smog test can anyone help

[djZuvuya]

failed the smog test and when the tech tried to adjust the mixture it would not bring the CO down we could make more rich but not lean it out. We eventually tricked the machine to get a sticker but would like to correct this rich condition. Last year when I had the smog test done it indicated that I was running lean, I have no real noticable indications of the normal culprites that would cause this problem to appear. I plan to look at air flow sensor, and check o2 sensor this w/e and see if they are gummed up. o2 sensor was replaced 11 months ago for hesitation at low rpm.

thanks for any suggestions

[Steve W]

It could be any number of symptoms. Most likely you have large air leaks around the intake manifold gaskets, some cylinders more so than others. Virtually all Carreras that have never had their manifolds removed leak a lot here. The O2 sensor trys to compensate for the lean idle condition, by richening the mixture to all injectors, but in doing so, while some cylinders run a little lean, others run excessively rich, causing wack with the CO mixture. Spray engine starting fluid at all suspect point with the motor running to detect all leaks. Disconnect the idle control valve and O2 sensor while doing this.

Or you could have clogged injectors causing some cylinders to run richer than others. You could try several treatments of injector cleaner in your gas to help it, such as Redline fuel injector cleaner or Techron.