Failed retest ca smog

Like title says I failed retest. I misplaced previous results but I will post current info Maybe someone has some idea. 91 4.0. Issues fixed since last test. Repaired hose from air box to vlv cover. Repaired other hose from vlv cover to intake. Replaced exh manifold with new banks header. Replaced 02 sensor with new bosh 4 pin. Ran jeep about 25 miles and at idle or 2k rpm for over an hour. Can't get pic to load here so I will just type info in. Only failed nox, at both 15&25 mph. Max nox at 15 mph is 711, meas 772 / max nox at 25 mph is 613 meas 772. Any ideas before I go spend more money than I have to. Thanx in advance.

have you put an aftermarket performance cam in the engine?has the engine been rebuilt where it is oversized bore or increased compression.. read the under hood label and where is states what emssion equipentment is on Jeep. see if it has TWC. that stands for 3way cat that does HC CO and NOX. you may have a bad cat. also if the engine is a high milage i have seen carbon build up that causes high NOX.what we did in that situation have run a combustion cleaner. get the engine real hot. spray the stuff in the throtle body while the engine is running . when the can is empty. shut the engine off let it sit ofr a couple of hours. restart and road tested and blow all that crap out of there. you may want to do it a couple of times.. hope this helps.

The cat is older. I have had the jeep for 6 yrs and never changed it. Nothing in the jeep for performance other than header. I was gonna replace cat but might try and clean the motor like you said. Will doing that effect the new 02 sensor?

we havent had any problems at the shop with o2 sensors doing the decarbons.the cat could be getting old and tired.

you got lucky with your banks header, when i smoged mine they looked up the smog number and it only registers for wranglers, not cherokee's. its a good thing he didnt look up the smog number until after he sent out the paperwork because he said it would be an instant fail. not to mention my banks header just cracked in two places on the tube that connects both collectors. cracked 3/4 of the way around on both ends.

jpcherokeekid said:

you got lucky with your banks header, when i smoged mine they looked up the smog number and it only registers for wranglers, not cherokee's. its a good thing he didnt look up the smog number until after he sent out the paperwork because he said it would be an instant fail. not to mention my banks header just cracked in two places on the tube that connects both collectors. cracked 3/4 of the way around on both ends.

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Dang dude. Mine was new in the box and said it was for Cherokee wranglers and camanche. Idk if it was the same with you but all I had to do is show them the sticker.

Banks header for 2000-2001 Cherokee .... http://arb.ca.gov/msprog/aftermkt/devices/eo/D-161-68.pdf

Banks header for 1991-1999 Cherokee ..... http://arb.ca.gov/msprog/aftermkt/devices/eo/D-161-68.pdf


For 91-99 you need part number 51305 for 00-01 you need 51306. They are legal for Cherokees

Think thats what I got I will dbl check. Thank for info.

i have the right part number for the year of my jeep. when i contacted banks about it they said the smog tag numbers were the same. now after the header cracked in two spots ( only had it a year and a half) they can shove it, warenty or not. and its not worth the hastle for me to deal with the smog issues to put a replacement banks back on. didnt not gain any performance over stock header anyways.
good luck with yours

When I go smog my Mustang I go to the CARB website and print out the PDF's that show what the parts I have are legal on. I just leave them sitting on my seat in case some jaskass tries to tell me it isn't leagl on my car. Print out the link I posted for your year and you won't have any problems anymore.