One thing no one mentions. Most cars should pass the sniff test without the
cat operating if everything else is functioning correctly.
KH

"L.W. ("ßill") Hughes III" > wrote in message
...
> Hi Mike,
> Like everyone has already said have it at full operating
> temperature, I run it down the freeways at traffic speed (80) for about
> twenty minutes and then let it idle to wait my turn to keep the
> catalytic convert hot at sixteen hundred degrees:
> http://billhughes.com/smog.jpg Of course do the normal maintenance, oil,
> filters, and plugs. And I did replace the convert about ten years ago,
> as that's it's job to chemically changes pollutants like carbon monoxide
> (CO), hydrocarbons (HC), oxides of Nitrogen (NOx) and particulate matter
> (PM) into harmless substances like carbon dioxide (CO2), nitrogen (N2),
> and water vapor (H2O): http://www.tifac.org.in/do/hgt/case/convert.htm
> God Bless America, ßill O|||||||O
> http://www.billhughes.com/
>
> Mike M wrote:
>>
>> My son's 89 6 cyl.Cherokee just barely failed the Ca. smog test. It
>> passed the 15 MPH but failed at 25 MPH on the "NO(PPM)" part of the test
>> (max allowed is 875 PPM.his read 1066 PPM). Anyone have any ideas what
>> the problem might be?
>> The mechanic told him it is probably either the O2 sensor or the
>> catalytic converter.
>> TIA
>> --
>> "Trust me, I do this all the time"
>> Mike M