1989 Jeep Cherokee. Its the Renix era 4.0. Took it to smog today. everything passed but my CO was almost double the maximum. I am running upgraded injectors (Ksuspension 12 hole injectors) but I don’t think that would cause it to fail right? I attached a picture of the sheet they gave me. I saw somewhere else that an o2 sensor could be the culprit but maybe someone else knows something I don’t.
test results. highlight is the failed portion.

 

Id be pulling all six spark plug for inspection. See if all look the same or is one or more look different than normal, thus pinpointing the bad cylinder, be it a spark issue or fuel injection issue. If all six look the same, then you may have a systemic issue, like the oxygen sensor. These are consumable, a failing sensor can even ruin a catalytic converter. Your NOx is high, so check the EGR for function and leaks. your catalyst maybe on way out If you install a pricey new catalyst, assure your oxygen sensor is fresh along with all other systems so as to protect the new catalyst from damage.

Make sure your MPS is working, no leaks in the vacuum hoses.
You can test the injectors, check for leaks, bad spray patterns.

My Renix XJ just passed, single digit values for pollutants

 

Best thing to do is move out of commiefornia.
Next best is to buy a REM so you can see what your jeep is actually doing.


Its been a while, but I didnt know there was a 12 hole that was recommended for renix... I assume you needed to change the FPR when you did them, just like going to a 4 hole?
X2 on pulling plugs and looking that them. If they are all looking rich you know you have a systematic problem, vs just one cylinder acting up. When is the last time it has had a tuneup?

 

I don’t exactly “tuneup” anything. If something is wrong I fix it, if something hasn’t happened in a while I’ll refresh the fluid, etc. When I swapped out the injectors I didn’t change the FPR (fuel pressure regulator is what im guessing you’re referring to) should i look into a different FPR? My uncle suggested some “guaranteed to pass” additive, but i haven’t looked into it yet.

 

A long time ago when the 4 hole upgrade was a big thing, a renix jeep required an FPR with a higher pressure. I see Ksus doesnt mention that on the 4 hole or 12 hole injectors, so thats a bit of a red flag unless theyre using a different part number/lower pressure injector? Might be worth emailing them to see what they say.

I would definitely check the plugs and if it hasnt been done in a while I would plan on doing plugs, wires, cap/rotor, and oxygen sensor. A throttle body cleaning and check all of the vacuum hoses to the MAP sensor/etc wouldnt hurt either.

 

Did you install the KSuspension injectors after your previous smog test? In other words, have you passed smog before with them?

Bear in mind, Renix Injectors flow 19#/hr @31PSI fuel pressure.