CA SMOG, HIGH NOx

[yossarian19]

anything like this in sacramento, CA ? hahaha. I have a bad feeling about mine this year...

It's an hour to Concord, but I've heard pretty great things about http://www.autoelectricandfuel.com/
People travel a long ways to train with those guys. When I was "in the biz" , the guys locally known to be good diagnosticians referenced Auto Electric and Fuel as the next step above.

 

[tetatdo]

Time for me to hijack the post to shed some light for poor jeeprocks. I am a smog tech who unfortunately owns a 95 xj 4.0 ho and currently pulling my hair out trying to fix my nox problem. It has always tested high nox barely passed the last two years. Smog done 12/18 initially failed nox 1000ppm. I knew going in failure was imminent. Replaced the cracked OEM manifold to cure the major exhaust leak and no major change in nox. Put a new walker "cal cat" direct fit in place of my damaged converter nox has no change. Tune up done with dealer parts runs great decarb services done normally etc etc.

Time to shed light:
Being cheap hurts!
Replacing my denso oxygen sensor with a OEM NTK brand sensor which is designed to switch at a faster rate than most others will. Jeeps are very dependent on a fast o2 sensor as there is nothing to help nox! If a sensor on jeeps is switching from rich to lean over 50 milliseconds its junk... mine is right on the treshold of junk... new sensor and retest with 91 octane tomorrow. I've fixed customers cars nox failures in the past using a better o2 sensor its all about the switch rate... lazy sensors create lots of nox problems.

Being cheap really really hurts!
Aftermarket obd1 cats are junk plain and simple whether its catco or magnaflow or in my case a walker brand.. for all you naysayers ill clue you in.. my local jeep dealer will send me a OEM mopar converter my cost is 900 vs your retail of 1400. There is a reason why the named above cats are under 400 installed... aftermarkets cats are not loaded with enough precious metals to combat a dirty jeep, jeeps are by far the worst in the industry for nox. OEM cats are a little bigger and are loaded up way more than any aftermarkets. I dont like spending money on cars juat for emissions but may have to go the OEM route.....

Until tomorrow one more test... $450 in parts at my cost and hours of labor which retails to cover $1250 at my shop

Hey man, looks like Im in the same boat as you. I just yanked my o2 sensor to replace it with a NTK and the old one was a brand new denso.

I am getting around 800-1000 for NOx at 25mph.

I just threw in the NTK unit and pulled the battery to reset the computer. Cat is brand new too.

Im kind of scared to run another test. Ive failed so many times I am finding it hard to believe the NTK sensor will do the trick...

 

[Bryan C.]

It's an hour to Concord, but I've heard pretty great things about http://www.autoelectricandfuel.com/
People travel a long ways to train with those guys. When I was "in the biz" , the guys locally known to be good diagnosticians referenced Auto Electric and Fuel as the next step above.

I will second this guy as someone to trust. I have taken my smog training with him. He has a smog training classroom, and an auto shop in the same building.

Swapping in a new cat in an attempt to pass smog is always a crap shoot. Best to figure out how much reduction is going on in the cat before just swapping it out. Before and after cat NOx and o2 readings are key to deciding if the cat is bad or not.


Back to the issue at hand. I fought a 2000 WJ a few years ago. It was a basket case and failed for NOx at over 1100 ppm. Had a plugged radiator, leaking water pump, and cooling fan was inop. Fixed all that, no change. Put on all 3 cats, the 2 mini-cats and the secondary cat. No change. Replaced oxygen sensors, no change. All factory parts mind you. I swapped in a MAP sensor and all of a sudden the thing passed. No codes, the MAP readings appeared normal, but changing it fixed the problem.

Just goes to show you, even with years of experience and training these high NOx failures are one of the hardest problems to repair. Just keep at it, it has to be something.

Another thing to note is in California you can get a 2 year exemption if you spend over $450 at a licensed repair shop to attempt to repair a non-tampered emission system.

 

[tetatdo]

Well, the NTK sensor seemed to help, but that wasnt enough.



I failed, but in the strangest way possible.

NOx 15 mph 69 PPM

NOx 25 mph 1000 PPM.


I have a feeling its leaning out at the higher speed, at 15 MPH the HC is 37, it goes down to 15 at 25 mph and the NOx shoots up...

WTF?!!

 

[markw]

What gears, tires? 1490rpm is lower than the rpm at 15mph. I'm guessing stock gears and tall tires? Another thing that will give you high NOX is a cracked header.

 

[tetatdo]

What gears, tires? 1490rpm is lower than the rpm at 15mph. I'm guessing stock gears and tall tires? Another thing that will give you high NOX is a cracked header.

stock gears and tires.

the header is new and with the elbows, no cracks,

 

[tetatdo]

stock gears and tires.

the header is new and with the elbows, no cracks,

changed the MAP sensor and retested. No change at all same numbers

NO 15 mph 24ppm
NO 25 mph 1105ppm FAIL


I think ive had it, ive been dealing with this crap since 2010. ive changed every part, some multiple times (cat, o2 sensor) nothing works.

I think the state of KKKalifornia wins. time to junk this peice of crap

 

[markw]

How old is the cat? How many miles on it?

 

[tetatdo]

How old is the cat? How many miles on it?

< 500 miles, brand spankin new magnaflow CA emissions

 

[yossarian19]

Do you have an IR temp gun?
If so, drive the jeep hard for a few miles & bring it back home. Crawl under it, shoot the IR temp before & after the cat. Try at a few different spots. What you want to see is ~100 degrees or more of temperature rise on the downstream side of the cat. Anything less tells you the cat isn't doing it's job properly. If it's more, your problem probably isn't the cat. I know you have a new one but it's worth checking before we resort to strong drink.

 

[tetatdo]

I actually tried that last week. Downstream of the cat was 115 deg hotter than upstream, so it seems that it is working...

 

[Dragonslayer]

Is your throttle body surgically clean? Remove the TPS and IAC and clean the throttle body until you think you could eat off of it. Check the throttle disk for carbon all around
the edges. Is the throttle disk closing fully? (check this both - while off of the car, and also when installed on the car)

What is the intake manifold vacuum Hg at idle?

If you're throwing in the towel trying to fix it yourself, then you might want to try
taking your rig to these guys: www.elmedicodejeep.com/

 

[tetatdo]

Is your throttle body surgically clean? Remove the TPS and IAC and clean the throttle body until you think you could eat off of it. Check the throttle disk for carbon all around
the edges. Is the throttle disk closing fully? (check this both - while off of the car, and also when installed on the car)

What is the intake manifold vacuum Hg at idle?

If you're throwing in the towel trying to fix it yourself, then you might want to try
taking your rig to these guys: www.elmedicodejeep.com/

The TB was kind of clean last i checked but it has been a while, I will take a look at it again today. I cleaned it last in 2012 and ive only driven the truck 1000 miles since then.

Where can I get a vacuum guage to check?

I have a feeling its starving for fuel at 25 mph, Im going to check fuel pressure at 15mph and 25mphs today, see what they are.

Does that shop you recommended do smog work?

 

[tetatdo]

Can you guys recommend a shop in SF Valley (near woodland hills) that allows multiple tests? The smog shop I was going to charged me 50 bucks, gave me 2 tests and said im done, i was livid about this.

 

[tetatdo]

Can you guys recommend a shop in SF Valley (near woodland hills) that allows multiple tests? The smog shop I was going to charged me 50 bucks, gave me 2 tests and said im done, i was livid about this.

So ive been doing some diagnosis today and fond something peculiar.

I replaced my FPR in 2012 with a new one, thinking that was part of the problem.

When I hook up my fuel pressure guage to check the pressure, at idle it was 29 psi, If I reved it, it went up to about 34 to 36 PSI and the pressure dropped. If I disconnected the vacuum hose, it would go up to about 37 to 38 psi.


While driving it the fuel pressure was 29psi idle and under load it would go up to about 34-36 psi max.


I still have my OEM Fuel pressure regulator, original from 1994. I popped it back in, and saw the pressure at startup and idle dead on 31psi, when I disconnected the vacuum, it went up to 40 psi and stayed there. I havent driven it yet to see whats going on, but Im about to.



Would this be the cause of my issues???

 

[Hellbent]

that could be it. your numbers have all been pretty good, except the NOX at higher rpm/load.
seems like you're going a little lean and the combustion chamber temps are getting too high.

 

[tetatdo]

that could be it. your numbers have all been pretty good, except the NOX at higher rpm/load.
seems like you're going a little lean and the combustion chamber temps are getting too high.

Guess what? There is a happy ending to my 4 year struggle with this smog BS...I can rest easy knowing i wont have to deal with this BS in 2 years. ITS FIXED

I GOT THE TRUCK TO PASS CA SMOG WITH FLYING COLORS! No funny business, no additives, nothing. Looks like the problem was with the fuel pressure regulator and possibly the o2 sensor.

I put in a NTK o2 sensor and the 15 mph test was clean, as you know from earlier posts. But when the fuel pressure regulator did the trick!!!

Also when I was originally testing it was almost 100 deg outside. Today I tested the weather was about 67 deg outside. I drove it around town normally for about 20 minutes. I didnt beat on too hard or overheat it..







These numbers are with a WJ manifold, K&N FIPK, 703 injectors and a Kolak exhaust! With CA Smog!

For future reference for anyone that has a 99+ WJ MAnifold or 703 injectors and a 180 deg t-stat. It is possible to get thru CA smog. My numbers are probably close to brand new jeep.

THANK YOU TO EACH AND EVERY ONE OF YOU for all your suggestions and help along this long and tedious process!

 

[Hellbent]

Awesome! Congratulations!
When I still had my '96, I was also running the 99-up intake, as well as the neon injectors-this was with a k&n intake, banks knock-off header, and dealership O2 sensor. It always passed with good numbers.
More proof that when EVERYTHING is working properly, a 4.0 should pass without issues.

 

[Four2score]

My turn to join the fun! '95 XJ failed in 2013. Smog tech told me to put a new cat on. Passed with numbers in the single digits! Thought I was good to go.

Fast forward 2 years later, NOX numbers are in the thousands. Tech told me my cat from 2 yrs ago was a $200 piece of just and should replace with oem. Called Jeep, $1,500, I don't think so!

So I went to a highly respected muffler shop and layed dow $450 for a good quality one. Numbers got worse. :huh:

The guys at the smog shop said it was running hot but the guage on the inst. panal said 210. They tried colling the engine down with a fan and same dealeo!

Going to swap fuel regulator, O2 sensors, and MAP sensor to see if that eliminates the problem. This is a spare vehicle so doesn't get driven very often. I should probably even run all the gas out of it and put fresh gas in but I can't beleive it would be that sensitive?

I think it is simply a part that wore out. Everything is clean with no exhaust leaks, new wires & plugs, & never had any problems really with the Jeep except a part wearing out and breaking here and there.

I wish these Jeeps had better computers that could flash a code and you could just change out the part it leads you to.

BTW, the smog tech told me to squirt a bunch of water through one of the vacuum lines while it is running and that could clear out the carbon build-up and make it pass. That sound Kosher???

 

[blondejoncherokee]

you really need to check for exhaust leaks. Like really well. you need to verify 100% there are none .

could be truly running lean, try higher flowing injectors possibly.

If you are 100% sure:
try colder plugs, colder Tstat, and replace the o2. I cant stress exhaust leaks enough. Also the coolant temp sensor as well. alcohol burns cooler, try like 4 bottles of HEET too. take it in cold as well.