txf54

Hey Y'all. Just tried to go smog my XJ yesterday, and I failed because my NO (PPM) failed at 1066. Apparently the max is 571... 🤦*♂️ Anyway, I think it might be the EGR valve clogged? Cracked manifold? Old plugs? Clogged injectors? I'm planning on switching the plugs and running a can of seafoam thru the system... just wondering if anybody else has had this problem. If anybody's got suggestions.. I'm greatful for it. A LOT. Thanks guys 👍

00t444e

We don't have testing here so I can't help with that but it doesn't have an egr. It could be a bad o2 sensor, is it throwing a code?

fb97xj1

Whats the mileage? The combustion chambers may be in need of a good cleaning (link below). When was its last tuneup? And when was the cooling system serviced last? Out of curiousity, what brand o2 sensors are you using? NTK is best. Aftermarkets dont always work like theyre supposed to.

ttps://www.cherokeeforum.com/f30/steam-cleaning-your-4-0-a-226299/

PatHenry

I have to guess CA... Even here in the People's Republic of MA once a car is 15 years old it's exempt from the emissions part of our annual inspection. Only in CA would they hit a 24 year old passenger vehicle with strict emissions standards.

Rambler65

High NOx can be caused by a too-lean mixture driving up combustion chamber temperatures. Add vacuum leaks to the list of things to check.

https://www.smogtips.com/failed-high...tric-oxide.cfm

txf54

Thanks for that link, that will come in handy. Since it's not equipped with an EGR, my guess is my CAT is bad. Gonna do a complete fuel system clean, new O2 and new CAT and see if that does the trick. I have the up most feeling it does work.
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4.3L XJ

I agree, the cat is worn out. There is a substance besides platinum in cats that reduces NOx. You will need to replace it. Also look into the upstream O2 sensor since you also might be running to lean

txf54

Thanks for the help guys, Ill start looking into some CATs, does anybody have any suggestions for what kind to get? Any suggestions for an O2 sesnor too?

4.3L XJ

What state are you in?

PatHenry

NTK brand on the O2 sensors. Per Cruiser.