My 2001 failed CA smog for high nox. What now?

[01_XJ]

I just got home from trying to get this thing smogged but it failed. I've attached a scan of the numbers to this post. The Nox reading at 15mph was the one that did me in. It was supposed to be under 517 and it measured 808. I talked with one of the guys there for a bit and he seemed to think it would be either carbon buildup on the pistons or an issue with the cat. He had recommended getting a bottle of the Guaranteed 2 Pass (which I did on the way home and already have it and a bottle of Heet in the tank).

I replaced the 0331 head back in August with a brand new casting because it had cracked, and while it was off I cleaned off the pistons pretty well. Would the O2 sensors have any effect on the Nox values? I had to replace one a few weeks backa nd have had my CEL come on and off a couple times since. When I hit it with the OBDII reader a few days ago it was showing i think 4 codes and they all had to do with the other 3 o2 sensors in there. Looks like I'm gonna have to replace them all, but I'm wondering if that even effects the Nox measurement.

Other than that, I got the engine warm, have recently changed the oil/filter, plugs were done with the new head, all new cooling system parts. I'm not really sure where to go from here. Do I let this G2P run through the system and try it again, or do I go replacing stuff?

 

[Fastdemise]

If you don't already know our late model XJs have 2 precats right after the header and the big one right before the muffler. But using anything named 'guaranteed to pass' sounds like a winner.

 

[XJWOLF]

The emissions are controlled by O2 sensors and the CAT. There is no EGR system so its o2 and CAT. You can test the O2 sensors but they are sensitive to voltage so a specific procedure must be followed. I doubt carbon build up is the problem. Do you have trouble getting on the freeway at RPMs above 3K? that's a sign of a clogged CAT. If the O2 went bad and you were running rich it would kill the CAT so it may be the CAT.

I've gone through this with my 95 YJ and have passed with tune-ups and new CAT, but last time is barely passed. I never did replace the O2 sensor. The XJ passes with flying colors. Has your mileage fluctuated recently?

 

[01_XJ]

The emissions are controlled by O2 sensors and the CAT. There is no EGR system so its o2 and CAT. You can test the O2 sensors but they are sensitive to voltage so a specific procedure must be followed. I doubt carbon build up is the problem. Do you have trouble getting on the freeway at RPMs above 3K? that's a sign of a clogged CAT. If the O2 went bad and you were running rich it would kill the CAT so it may be the CAT.

I've gone through this with my 95 YJ and have passed with tune-ups and new CAT, but last time is barely passed. I never did replace the O2 sensor. The XJ passes with flying colors. Has your mileage fluctuated recently?

mileage fluctuates between s**tty and very s**tty . Seriously though, it's usually about 15 city/16-17 freeway. The o2 sensor I replaced actually had the wires ripped out of it somehow. I saw the check engine light come on and finally got under the jeep to look at things and found the two wires from the lowest o2 sensor just hanging there. Somehow they had ripped out right at the end of the sensor. I replaced that and the CEL went away briefly, then started comig back. Maybe the wires touched something and messed up the other sensors? It was a bit gutless getting recently since I had the o2 sensor issue. One of the codes it was giving me was for the o2 sensor heat circuit, and the guy at the shop said that that code is pretty much a sign that the sensor is bad.

As far as the cats, should I look toward replacing the precats or the main one? Or should I replace the sensors first and try the smog again first?

 

[jeeptec]

i would replace the defective o2 sensors. also i believe the cats are 3way. that means they are designed to reduce the CO,HC and NOX. i know you have to buy the complete assembly from Jeep. try the sensors first. drive it get it good and hot then have the shop do a pretest.

 

[Boatwrench]

PM Rightseatsis. She was having issues with her 01XJ, actually talked about selling it and finally did some repair to the exhaust stream (replaced pre-cats?) and it passed with flying colors.

 

[01_XJ]

i would replace the defective o2 sensors. also i believe the cats are 3way. that means they are designed to reduce the CO,HC and NOX. i know you have to buy the complete assembly from Jeep. try the sensors first. drive it get it good and hot then have the shop do a pretest.

Gonna try those first since I'm betting they are quite a bit cheaper than buying any of the cats.

PM Rightseatsis. She was having issues with her 01XJ, actually talked about selling it and finally did some repair to the exhaust stream (replaced pre-cats?) and it passed with flying colors.

Thanks, I'll shoot her a PM.

 

[01_XJ]

looks like i'm gonna have to get temp tags for now until I can get the stuff done. It sucks that CA started charging $50 for a 60 day temp tag now.

 

[rightseatsis]

Boatwrench told me about this thread. I just went through this with my 2001. I could not keep the CEL off after the jeep got hot. I was also having problems w/the oil pressure dropping to almost 0 at idle when hot. At first the dealer I took it to said it was the oil pump but ended up just putting in heavier oil, it helped. Then I still had the CEL so I decided to bite the bullet and take it into a local exhaust shop. Was I lucky, the shop owner had worked at the recently closed Jeep dealer, he knew the problem and had bought all their old inventory. I ended up getting the 2 precats and the third large one for $850.00 including labor. The jeep ran cooler and the oil pressure problem went away. Drove it for about 100miles and then passed the smog with nice low numbers.

I was almost thinking of selling it I was so frustrated but I ended up spending about $1000 to keep it running. Now I am planning on taking it to Fall Fling.

 

[srmitchell]

That's a great deal.

My 01 passed fine, it has new injectors, and new upstream o2 sensors.

Run a good fuel system cleaner.

 

[01_XJ]

Thanks for all the input everyone. I ended up changin out all of the o2 sensors since they were all original and at least one of them had gone bad and apparently made a fuse blow. I ran some seafoam through it, along with 2 bottles of G2P (guaranteed 2 pass). It was idling and running a bit better after the o2 sensor change so I was hoping it would pass this time. I just went to smog it and it ended up failing again. The numbers actually ran a little higher than last time which I think is from some fo that g2p being in the fuel still. either way, my NO numbers are still really high. Called the stealership and they want $699 for a new main cat. What should I look at doing now?

 

[streetxj]

I think you should replace the precats. Worse case scenario, you will also have to replace the main one also if it fails again. Reason being, the precats are right under the headers and receive all of the pollutants from the engine. The exhaust that reaches the main cat, is cleaner from processing through the pre cats. So most likely, it's your precats that are dirty and not filtering the pollutants properly. Depending how long it's been running like that, is how dirty the 3rd large cat can be. Actually, when I think about it again, you should replace all three to get the inspection over with.

California and their emission laws.. assgas:

 

[01_XJ]

Yea it would be nice to be able to afford to do all of the cats, but it's not an option right now. I think what I'm gonna have to do is "move" to a non-enhanced area (where they don't test for NO), get it smogged, then "move" back.

 

[streetxj]

I think that will be a better option^. California's high cost of living and really high gas prices = no fun unless you have $$$. I know florida is one of the states that doesn't require emissions testing.

 

[01_XJ]

I think that will be a better option^. California's high cost of living and really high gas prices = no fun unless you have $$$. I know florida is one of the states that doesn't require emissions testing.

lol, I actually meant going somewhere in CA that doesn't do the "enhanced" smog test where they put it on the dyno and run it at 15/25mph. I was living up in central CA a couple years back and SLO county is not an enhanced area so all they do is rev the engine. The difference is that on that test, they don't check the NO levels which is what is causing me to fail.

Yea CA emissions suck, but I can't really see myself ever moving away from here.

 

[CharlesS]

Have you tried adding ACETONE to your gasoline before going in for the smog check? By adding 1 oz of acetone to 10 gallons of gasoline the acetone will break the surface tension of the gasoline molecule which aids in full vaporization to provide a 100% burn of the gasoline.
There are reports of adding 1-3 oz's of Acetone to 10 gallons of gasoline that have lowered emissions by as much as 60%. The unburned gasoline is what causes the higher emissions.

Several years ago I had a '00 4.0L Ranger with alot of performance modifications which failed on the smog dyno. The tech said, "Bring the truck back when the problem is fixed and I will test it again for free.
Since I only lived a few miles from the station; I went home and added the acetone to the gas tank and drove around for 15 minutes before going back to the smog station....
When I drove up the smog technician said, "if the vehicle fails this time; you will need to pay for the next retest....
Once the smog check was over the technician walked over with an amazed look on his face.
I asked him if I passed and he said, "YES.... with flying colors...."
"What did you do to resolve the problem?" My response was "I just fixed the problem". The technician asked, "So what was the problem?" My response was a polite... "It doesn't really matter as long as it passed."

 

[z06elmo]

how many miles are on your 01 XJ? The main thing is to get the car and cat really warmed up before a smog. I'm surpised the G2Pass and the seafoam didn't help out. When all else fails you have to change the cats. Check Magnaflow - they make approved california cats for much cheaper than factory.

 

[streetxj]

Have you tried adding ACETONE to your gasoline before going in for the smog check? By adding 1 oz of acetone to 10 gallons of gasoline the acetone will break the surface tension of the gasoline molecule which aids in full vaporization to provide a 100% burn of the gasoline.
There are reports of adding 1-3 oz's of Acetone to 10 gallons of gasoline that have lowered emissions by as much as 60%. The unburned gasoline is what causes the higher emissions.

Several years ago I had a '00 4.0L Ranger with alot of performance modifications which failed on the smog dyno. The tech said, "Bring the truck back when the problem is fixed and I will test it again for free.
Since I only lived a few miles from the station; I went home and added the acetone to the gas tank and drove around for 15 minutes before going back to the smog station....
When I drove up the smog technician said, "if the vehicle fails this time; you will need to pay for the next retest....
Once the smog check was over the technician walked over with an amazed look on his face.
I asked him if I passed and he said, "YES.... with flying colors...."
"What did you do to resolve the problem?" My response was "I just fixed the problem". The technician asked, "So what was the problem?" My response was a polite... "It doesn't really matter as long as it passed."

^Interesting info.

 

[01_XJ]

how many miles are on your 01 XJ? The main thing is to get the car and cat really warmed up before a smog. I'm surpised the G2Pass and the seafoam didn't help out. When all else fails you have to change the cats. Check Magnaflow - they make approved california cats for much cheaper than factory.

my xj has about 220k on the odometer. I drove it around for about 15 min before the test and put my foot in it a bit whenever possible. It was at full operating temp by the time I got there. I'll check out those magnaflow cats.

 

[z06elmo]

220K would be about the life expectancy for factory converters. I would think the main cat is the one piece you need to take out most of the emissions. I'm not sure what the function of the precats vs. main cats are. I wonder if one is concentrated more on NO2 and the other CO etc. Maybe you can find a used header at a junk yard for the precats and the magnaflow for the main cats.