mysteriousgyrl

fail emissions no2 ( or something like that). It was basically double the limit it should have been. everything else passed. any ideas of where to start looking first? Thanks in advance...

1SlowFormula

well what is done to your car? do you have a cat? are your O2's up to spec?

Need more info please, now is not the time to be mysterious... hehehe

mysteriousgyrl

yes it has a cat, i just had one o2sensor changed 2 weeks ago but I found out today there's more than one. and i had a egr (or something like that) valve replaced last week before taking the test. They did the tail pipe test. Sorry not real good with cars or parts..

valter

Engine can be running lean to get high NO2. Most likely it's bad O2's or EGR not functioning properly.

EnerjetF67

Usually when one fails for NOx the culprit is the EGR, possibly an O2 sensor but usually O2's going bad cause richness, not lean which would cause high NOx.
When an O2 is bad, usually one would fail for HC/CO not NOx.
Thank god I'm in Michigan where we have absolutely ZERO emission testing !

1SlowFormula

Here in PA you aer exempt if you can keep the milage below 5K per year...

That's pretty easy to do if you have 2 gage clusters.

96flame

Is the car stock or do you have headers on it, aftermarket tuning. Nox can be caused by too much ignition timing, lean conditon, too hot combustion chambers. The key items used to control Nox are the Catalytic converters and EGR system. Its possible for cats to fail only on Nox but EGR is usually the culprit.