Passed the sniffer...now i'm failing it...

Had the XJ inspected a few weeks back and I passed the sniffer and everything else except the exhaust manifold had a crack. I had that welded, and re-installed it with a new gasket. Now the manifold passes but they said i dont pass the sniffer now. Last time i took it in on a warmed-up engine. This time i left it overnight for them to do when they got to it. Does that make all the difference? Also, in re-installing the manifold i routed the wire for the knock sensor wrong and it lays against the intake manifold now. Will the comp pick up vibrations from the wire being like that and then decide it's knocking thus making the mixture richer?

Yes, warm it up as hot as you can before you take it in. Most states advise you to have it warm before you take it in. Does your state have state run inspection stations or do you take it to any certified garage? I'd make an appointment for the sniff test and show up as close to the time as possible. If they delay in testing you then take the car out and warm it up again. Good luck.

YEP. Get it warmed up all the way. 15-20 minutes. In S/W Ohio we have a sniffer test. They have big signs telling you to NOT to shut off the engine while waiting.

I always thought it was a conspiracy to pollute the air even more while you are waiting, hence validating the need for the test.

My son's CJ8 has one of those weber carbs that shouts "not for use in Calif. and not for use on any pollution controlled vehicle" on the marketing literature. He passed smog with 2 out of 6 plugs fouled - but fully warmed up. Go figure.

Incidently, the most common reason for failing smog is a bad O2 sensor, but it could be any number of other things. Year, mileage, codes?

Well, i got some more info from the tech today. He said that my hydrocarbons were just a little high, and that an oil change or some fuel cleaner should fix that. But he said that my CO was through the roof. What does that tell you? O2 sensor? EGR? I'm clueless.....