CA smog issue please help

88 4.0 100K miles Didn't pass CA smog immisions out here today. I hate to get rid of the jeep, but if I can't pass smog after fixing its gotta go.

It passed visually, but didn't pass on the CO2 test. I guess thats the

O2 sensor and everything else test. The numbers were high the tech said. Gross polluter.

I read threads saying to replace the O2 sensor first.

here is what I have did and found.

when I bought it the oil smelled a little like gas. I didnt change it yet.
The fuel was a little turpinetined less than 1/4 of a tank. I added fuel additive several times and toped it off with 91 octane , smells fine now.

I gave it a tune-up, new cap, rotor,plugs. The wires looked good
everything else is original. Runs a little rough like a misfire sometimes, also when I punch it it stumbles and sometimes dies. At idle only.

I was told:

change the oil
run original copper plugs( I used double platinum by mistake)
change the O2 sensor
clean and check PCV
clean and check EGR and hoses to EGR


What else should I do .

I really want t o keep my cherokee.

Post up your numbers. What were the limits for each and what did you pass/fail at?

Replace the plug wires while you're at it. The 02 sensors only last about 60,000 miles. Replace it. There is no PCV but carefully check the integrity of the CCV hoses from valve cover to manifold and air box.

change the oil asap, if it smells at all like gas it is contaminated and isn't going to keep it's viscosity. Keep driving it as is and you're signing the death warrant for every bearing inside the motor.

Usually when you have gas in the oil it's due to an injector leaking into the combustion chamber and pouring gas into the cylinder. did any of the plugs you pulled out look worse than the others? or wet and smelled of gas? you could also pull your new plugs one at a time and smell them, if you have an injector that's leaking into the cylinder one of them will come out wet and smelling like gas or have more carbon buildup on it than the others. Since you mentioned that it stumbles when you step on it from idle I would be strongly leaning towards a bad injector as the source of your failure. Your motor will run best with Champion copper cores in it, the correct plug number for your 88 is RC9YC.

If your injectors are all metal they are most likely original or very old, the updated ones are combination metal and plastic bodies. The all metal ones are notorious for leaking and causing engine fires, so if they are all metal except for the electrical connectors I would change them out regardless of whether a leaky injector is your problem or not.

The oil will be the first. The second is the plugs and wires. and O2 sensor. The last will be the injectors. I'll do all of it before the next smog for sure.

Number are that failed
15 mph NO (PPM) 3100
25 mph NO (PPM) 3106

Sorry I thought it was the CO'2 but looks like the other.





Thanks guys.

also look at the MAP sensor and all other vacuum lines.

Check all vacuum lines, replace plugs, o2 sensor, and clean sensors.

I had a leaky injector for a while, and I totally gained power/smoothness once I had 6 perfect ones again.

can anyone tell me where the MAP sensor is on the cherokee?

How about other sensors and how to clean them?

the map sensor is on the firewall just to the drivers side of the valve cover. it has a green plug and a vacuum line running from it to the throttle body.

So you guys think if I add
new injectors
new O2 sensor
New plugs
Clean MAP sensor
New oil.

I should pass the smog test?

I have a ’88 Renix and I am a Schooled Renix Tinkerer.
My advice is to read, test, diagnose problem point then decides what is necessary to correct problem before wasting money on parts in hope of a quick fixes.
If you are willing to do some research below is a starting point.
Many W-Sights on Jeep Renix
Renix Multi-Meter Troubling Shooting
http://www.cherokeeforum.com/showthread.php?p=11696

Good luck from DJ

Just what I was looking for. Thankss for the site .....

I am for sure buying new injectors though and aa new O2 sensor. I'll check the rest with the multimeter as suggested.

Great site once again and thanks guys......I'll post my results when I fix the culprit.

Ecomike posted: Testing Jeep O2, Oxygen sensors – first posted 10-24-2009, 4 Pages of info
http://www.naxja.org/forum/showthread.php?t=1012701

Good luck from DJ

Well after changing the O2 sensor, new plugs, new MAP finding a cracked vacume line, looked at all the vacumme lines, it still is not a steady idle . It goes up and down a little ,but doesnt stall. It will flucuate the motor like up a little then down a little.

What is this idle issue? EGR valve.

Injectors? I'm waiting for the new ones to come in still.

Other than that it runs like a champ, but won't passs smog. They said NOX to high.

Some morning with the engine cold, snug up your intake manifold bolts. They'e known to work loose.

I'll try that in a few minutes. I havent fires it up in about 3 hours and it only ran for about 5 minutes. Or I'll do it in the morning.

Thanks.....what doe you guys think about the EGR valve. Could this be the culprit?

So I tried the test for the EGR valve . Here is what I did.

I pulled the electrical connector off the EGR vacum solenoid and it didnt change the engine idle at all. It still was studdering and fluctuating at idle like a vacum leak.

Do you guys thiink its the EGR valve or TPS?

I'm stumped at this point.

The EGR valve can leak internally whether it's being actuated or not. Why not pull the valve off and verify it is seating/sealing correctly?

I think I'm going to just replace it for a precaution. The jeep sat in the desert 100 plus degrees for about 3 years before I bought it. It was in a tow yard.