Among the simpler things to check if the NOx is high is the following: Timing: base, mechanical advance, and vacuum advance Temperature: slipping belt, corroded impeller, stuck thermostat, bad otterstadt, blocked radiator (air side AND coolant side) mineral deposits in motor affecting heat transfer, air pockets. Excessive carbon build-up in the combustion chamber. High NOx is caused by high combustion temperatures (pressures) so anything that would cause the combustion temperature (pressure) to increase is a possability. A catalytic converter by itself does not change NOx unless it is plugged up. In that case it causes increased back-pressure raising the combustion temperture (pressure). A simple test can confirm. A symptom of a plugged Cat is a drop-off in power on acceleration or a glowing Cat. I am sure Gregg can offer much more expert advice on the subject of emmision control but this is what I offer. David Teitelbaum vin 10757 --- In dmcnews@xxxxxxxxxxxxxxx, "stephenjpattison" <steve@xxxx> wrote: > > > My car seems to frequently fail the Nitrous Oxide test on the > California Emmisions Inspection. I have 31k miles and recently had > the O2 sensor replaced in Garden Grove. Outside of the repair shop, > does anyone have any ideas what I might look at ? Levels today were > 2 to 3 times maximum allowable. > Thanks To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnews Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/