Hi All!

This is my first post here but I'm no stranger to the info here. I wanted to start by extending my sincere appreciation for all the information shared here! When I got my Jeep I told myself I would do as much of the work myself as possible, and with this site I've luckily been able to stay true to that!

Onto my issue:

I just my stock 1997 XJ smogged and it failed. It *barely* passed on all the readings except NOx, where it doubled the allowable. Before getting into the results, I should mention I was only run for about 60 seconds before sitting for 90 minutes at the smog test place down the street - so it was pretty much cold. Results below:

......................CO2.....O2.......HC......... ......CO%..........NO ppm
...........RPM.......................max_meas..... max...meas...max meas
15mph..1394... 14.10__0.4___54__51_____0.69_ 0.43___527_1028
25mph..2227... 14.20__0.3___38__38_____0.83_ 0.50___780_1428

The man in the smog check place mentioned that the measurements (except NOx) show that the cat is close to needing replacement.

Is that correct?

From the research I've done, I've seen that NOx isn't related to the Cat so much as much as running lean, bad sensors, etc.

I've read about running the car pretty hard for 20 or 30 minutes before the test to help get it hot, then running premium gas and "Guaranteed to pass" fuel additive.

Changes in the last 6mo/10,000 miles: distributor, ignition coil and crankshaft censor replaced 2 months ago (working through a no-start issue). Replaced plugs and cables just before Christmas (about 10,000 miles ago). The plugs I put in were Champion Copper.

Premium much the only think I haven't replaced is the rotor cap.

I have one free retest within 30 days with the place I went, so I wanted to get everyone's thoughts on what I might do as a next step.

Thanks for your time!

 

"so it was pretty much cold."

Can't be, has to be @ operating temperature i.e. closed loop. Any codes or CEL? Did it pass last time?

 

Why is a 97 being tested that way? It should be a obd test. As for The Nox levels being that high. I would say yes you need a cat. Your EGT are getting to hot and is not having the proper flow out the tail pipe. Removing the catylitic converter as I have heard from guys in the diesels say. It lowers The EGT. So my bet is your cat is bad or clogged.

Catalytic Converter Problems

A vehicle's catalytic converter helps remove NOx from the exhaust before it gets to the tailpipe by passing the gases through a titanium oxide membrane. A defective catalytic converter can then result in elevated NOx emissions. This is especially a problem in vehicles that don't have exhaust-gas recirculation(EGR) valves, since they rely more heavily on the converter to deal with NOx emissions

I hope this helps as I'm a emissions tech here in Utah.

 

Yeah, I found that out about being cold during my research after it failed, haha! Had to take it in after a lunch meeting to the smog check place 3 doors down from my office after sitting since morning.

No CELs - Meant to mention that in my original post.

Yes it passed last time. I recall it passing with flying colors, but that was 2 years ago so I might be remembering wrong. I also know that last time, I was driving it for my whole lunch break before dropping it off - and they didn't have anyone ahead so the test was started when it was hot.

Last think I meant mention: I definitely am in need of an oil change.

Thanks!

 

Thanks for the cat info! As for the mention of the "ODB test", not sure what that means. Forgive my ignorance - still have a lot to learn when it comes to cars/jeeps.

In regards to replacing my cat, here's another set of questions: the one that's currently on my jeep is after-market (slip fit as opposed to the bolt-in OEM with the flange.

Looking online for replacement slip-fit ones, I see there's different inlet/outlet measurements. Most online are symetical (2.5" inlet & outlet), but when measuring the one on my Jeep, the inlet and outlet are different. See photo:



Can I make a 2.5" outlet work if I clamp it on the OUTSIDE of the muffler inlet rather than the 2.25" which tucks inside it?

I found a Catco with the proper inlet/outlet dim's from Summit Racing, but it's about $100 more than Magnaflow's with 2.5" on both ends...

Thanks!

-BB

 

Here in CA all smog tests are done on the dyno roller machines. The only cars that are OBD tested are full time 4WD and AWD.

 

So your telling me, a 2010 whatever gets the dyno? Yep gay.

 

In 2016 it will. No smog checks the first 5 years but then it's dyno. It is pretty gay.

 

Ah. Utah is every other year it gets safety emissions for The first 7 yrs. But here if its 96 and newer it gets obd. 95 and older gets a Two Speed Idle(TSI) No more dyno here. I did pick up my works old emissions machine for free. So I can pretest my own vehicles emissions before I take them to my work for the real test. Bwahaha.

To the OP good luck.