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Old 09-09-2012, 05:36 AM   #7
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What I Drive: 2005 ZX4 ST

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Originally Posted by sailor View Post
FWIW, BC's got the right idea!

it's been discussed in the "tuning" forums - IF both cat sensors are working properly, the 'downstream" one needs to see "cleaner" exhaust than the "upstream" one to let the computer know the Cat is functional.

SO, 'cheating" by moving the downstream further out of the exhaust flow, like by screwing it into a "spark plug anti-fouling" adapter will "fool" the computer, letting you "pass" emissions testing....

You said exactly the words that I needed to hear. I have an extra bung welded into my exhaust manifold after the flex pipe. I am going to try moving the rear O2 back there and see if it reads any differently. Hopefully that will at least get me to pass inspection so I can have a bit more time to scrape some dough together for the new exhaust manifold.

BC, I guess you are right that the cams will not change it. After hearing your explanation, I realize that I was hoping the cam swap would be a less expensive alternative to replacing the exhaust manifold.

Either way, I plan on selling the car once its fixed up and most people don't want an idle that lopes from 650-850 on a stock tune. It purrs well on the aftermarket tune at 1000rpm, but can't pass inspection that way. NJ and EFI cars are a bad combo for enthusiasts.
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