• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Failed emmision test: high CO

O

otto

NAXJA Forum User
Location
seattle
1990 XJ 4.0, new Bosch 19# fuel injectors, flowmaster 50 exhaust, working EGR valve and new CCV plumbing.

I've been reading other peoples' reports of failed emissions tests trying to get a clue about why I failed with very high CO readings at cruise and idle. CO levels are 5X higher than limit. Obviously two possiblities come to mind: O2 sensor and cat. Do the high CO levels point to one or the other? HC level also failed, but was just over the limit. Thanks for any help.
 
Same thing happened to me. I replaced the cat and was good to go. Is the cat the original. Does it rattle or do you hear a rattle after you shut it down?
 
No, no rattle, and the cat's been replaced once. The first owner of this XJ failed test twice, both times a new O2 sensor did the trick, but these high CO numbers have me thinking cat too. I'd hate to drop $50 on the O2, fail the test again, then have to install a cat. Ah, the joys of owning a 15+ year old vehicle!
 
I'm willing to bet it's your 02 sensor. I just had my '90 go through the same thing. Your cat will clean up the HC's at higher rpm's as it gets hotter. But the high CO's need to come down first.
Try finding a smog station that will do a free retest, or some will even do a free pretest (at least here in Ca.)
 
Yeah, WA state gives ONE free retest, so I'll take the easy route and change the O2 sensor and plugs first before I drop cash on a new cat. It's gettin downright expensive staying on the road!

And thanx EXPEDIENT for the PM advice. I'll give it a try if I still can't pass.
 
It's just a band-aid but it really works.
I pulled nearly ZERO emissions numbers in my 91 and 93 oldsmobiles and my 91 XJ after running this little red and yellow bottle of RXP for a few days before inspection. If somebody doesn't believe me I saved the print-outs they give you at the end of the inspection line. They even looked under my car to see if I re-routed the exhaust.
My brother ran it in a crappy chevy cavalier that failed miserably the week prior. It didn't run zero numbers but it honestly passed the next time through.
And that's just my 2 pennies worth
 
The best thing you can do for emission tests is that you run teh vechial a lot before take the test. If it is a 97 or newer then you you have to make sure the PCM rums through its testing cycles. On older cars (especially colder days run the car up and down a highway at least twice.

It sounds to me it's an 02 sensor. The only thing I wonder is if you are getting high readings from the 02 sensor before or after the cat? If it is the one before then it is the sensor. If it is bank 2 then it might be the cat.
 
took my jeep to get inspected after being in hawaii for 7 years with no smog regulations was really worried about failing here in california. what I did add one bottle of lucas fuel treatment and 91 octane gas. drove around the day before to get that stuff through the system. when I got to the station there was a car in front of me, so I left mine running until it was ready to be tested. when tested passed with flying colors
 
Casey C said:
It sounds to me it's an 02 sensor. The only thing I wonder is if you are getting high readings from the 02 sensor before or after the cat? If it is the one before then it is the sensor. If it is bank 2 then it might be the cat.
Click to expand...


IIRC, his 90 xj won't have an 02 senser after the cat.
 
Yes, 1990 (RENIX) only has one O2 on downpipe.

Changed it out yesterday and passed retest this morning with low numbers.

Before I did the change I noticed JEEP had a miss under load, like fuel starvation, but only when cold. Cleared up after 3 minutes of driving after engine reached operating temp. New O2 took care of that.
 
You must log in or register to reply here.

Similar threads

9
1990 Renix SMOG, CA problem with running Rich/Lean
2 3 4
Replies
68
Views
8K
Ecomike
Ecomike
M
Failed emissions test, extremely high HC
Replies
3
Views
370
blondejoncherokee
blondejoncherokee
ParadiseXJ
High CO in CA - smog help!!
Replies
10
Views
858
blondejoncherokee
blondejoncherokee
G
Another Failed Califorina Smog Thread
2
Replies
35
Views
2K
Ecomike
Ecomike
B
Cracked block or bad oil ring?
2
Replies
39
Views
2K
blistovmhz
B
Back
Top