Any of you have an idea?

[frontman]

All advice is welcome. Failed smog retest today. Just nox EVERYTHING else passed with flying colors. Can't upload with this stupid IPad so I will just give u info. Just changed exh man with new banks header. Changed 02 sensor, replaced hoses checked vacume lines. Newest results are as follows... Man nox at 15 mph is 711 / my meas 772. Max nox at 25 mph is 613 / my meas is 772. Any help is appreciated. Btw the cat that I have has been on at least 6 yrs as I have owned it for that long. I know it wouldn't hurt just wanna find out if there is something else I could do before I go retest. Someone in the oem section said to use cleaner in the throttle body but I'm afraid it will jack the new 02 sensor up. Thank in advance. I'm not one of those tools that will argue with you when you give advice so all is welcome. Thanx

 

[Mike1331]

Did you drive around for at least an hour to get the cat hot before testing? If so try that next time. And if you suspect your cat is on the verge of taking a shit drive in on the freeway for at least an hour to make sure its good n toasty.

 

[Jeep450r]

Yeah try running on the freeway right before the test to get the cat nice and toasty.

I learned how to read/diagnose all of this stuff back in my auto class last year. Unfortunately, I forgot it all lol.

 

[Forceful Llama]

Leave it idling in the parking spot if you can too once you get it hot. Suck to get there and then have to let it sit and cool off before you could test.

 

[buildingonabudget]

Having the same problem on my buddies XJ. HC's are good but Nox is way high. Here are some things I did that did not help it:

Full tune up
OBD2 cat
Seafoam (do it b4 tuneup)
Cooling down in the parking lot for 2hrs
Driving 30 miles before test and letting it idle in the parking lot

Next we're going to try the o2 (I doubt that will help) and MAP sensor.
Ill keep you posted and see what happens

 

[blondejoncherokee]

02
map
cat

seafoam the intake, acetone in the gas tank, then change plugs , air filter, cap and rotor after the sea foam.

check all exhaust manifold bolts for tightness.

 

[buzzbombxj]

check out your egr system. thats its purpose, to keep nox down by recirculating exaust gas into the chamber.

 

[Alex E]

check out your egr system. thats its purpose, to keep nox down by recirculating exaust gas into the chamber.

X2, check EGR or the cat, Nox is formed during high combustion temps. Make sure your not running lean, have vacuum leaks, that kind of stuff.

 

[frontman]

Having the same problem on my buddies XJ. HC's are good but Nox is way high. Here are some things I did that did not help it:

Full tune up
OBD2 cat
Seafoam (do it b4 tuneup)
Cooling down in the parking lot for 2hrs
Driving 30 miles before test and letting it idle in the parking lot

Next we're going to try the o2 (I doubt that will help) and MAP sensor.
Ill keep you posted and see what happens

Thanx

 

[frontman]

Thanx for the input. I will try all suggestions. Done failing for sure.

 

[NorCalChris]

how hot are you engine temps? nox is created by heat.

 

[frontman]

I checked with a calibrated temp meter and it was running between 180 and 185. Jon if I run the sea foam with the new 02 sensor will it mess it up? I will look at the egr and map today. Think I will still do the cat just to be super sure. I used the jeep last night to get some wood up in garden valley and driving up and down the mountains with the wood got that cat super hot. I could defiantly smell it burning off junk. Still worried its bad. Should I install the cooler t-stat too since it runs so hot?