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2000 XJ Failed Colorado Emissions high CO

osue077

NAXJA Forum User
Good afternoon,
I purchased a reman 4.0 Jeep engine for my cherokee on Dec 6
I have installed the motor and it is running great. Initially I was getting 0132 code for high voltage to O2 sensor 1 bank 1. I changed both of the sensor and continued to get the code with that new sensors. I checked the wire harness from the o2 sensors up to the ECU for pinches or wire issues and did not find any. I cleaned all the grounds on the block and battery. I put the old sensor back in and began to get the 135 code for heating element for o2 sensor. I checked the fuse and it was popped. I replaced the fuse and put the new 02 sensor back in and drove with no CEL. With the new motor, I have replaced IAT, Cam Sensor, MAP, TPS, eng temp sensor, Idle control valve, spark plugs.
I have checked the intake manifold with starting fluid to verify that there are no vacuum leaks including plugging the PCV on the manifold. I went to the emission testing station today thinking I was good, to renew my registration and it failed the Carbon Monoxide test 19.7 GPM with the limit of 15.0.

I have no CEL, I have driven just over 500 miles on this motor and changed the oil today prior to the test. I pulled the spark plugs and there is no soot on them, just a very faint tan color on the insulators. I also changed the fuel injectors to the original Jeep injectors from the Ford multi hole injectors with no change on the reading on the o2 sensor.

What suggestions do you have for me to try next. I am going to replace the O2 sensor just to verify that is not the issue. The engine runs great so I am at a loss.


Thanks for your time.

Travis
 
What brand O2 sensor did you buy?

Is your XJ Federal or CA emissions?

High CO is from running rich. Double check to make sure your MAP, TPS and CTS are operating within spec.

Cheap, Made in China, sensors have been reported to be of poor quality and faulty ootb.
 
I think its called the oil pump drive shaft. Did you have it 'timed' with a SRAM tool? According to the FSM it times the injector firing timing. Also, what spark plugs are you running?
 
I have a Bosch O2 sensor. Non CA emission. I have replaced the MAP, TPS and CTS - I show all of them responding correctly.
I lined up the Cam Sensor using the toothpick method. I have the autolight copper core spark plugs.
 
I have a Bosch O2 sensor. Non CA emission. I have replaced the MAP, TPS and CTS - I show all of them responding correctly.
I lined up the Cam Sensor using the toothpick method. I have the autolight copper core spark plugs.

I would replace the Bosch with a NTK (NGK) O2 sensor. The Tooth pic keeps the shaft in place. As to the FSM, the rotation of the shaft needs to be checked with a SRAM (??) scan tool. I need to do this with mine. Something I am looking at is using Iriduim spark plugs. I put in a set of Autolite XP985. I think I need to go to Autolite XP5224, as I am at 9.45 static CR. If your spark plugs are new, then I'd wait to see if other issues are the cause. Also, I am looking to find an NGK Iridium spark plug to use. I do see some list an NGK2477 Iridium as a replacement. I am nut sure of its heat range.
 
I always do the "tooth-pick" method, there is no requirement for a scanner. Iridium plugs are just a waste of money, the 4.0 loves a standard copper plugs .
 
I've had only moderate luck with Bosch O2 sensors. They seem to work but only for a short while. I had to replace mine every 2 years prior to CA smog test in order to pass. Switched to a NTK and have passed my last 2 smog tests.

Ditto on standard Copper plugs.

Do you have a OBD 2 scanner with live data? You'd be able to see fuel trims, O2 operations and a few other things to narrow down the source of your rich condition.
 
I also recommend the NGK O2 sensor and also the need for genuine Mopar sensors. In dyno runs I have tested platinum, iridium, and E3 plugs (which were a complete disaster) and I run a MSD Dis4 set-up on my 2000.
 
I forgot to add I have also tested/verified my cam sensor timing (toothpick method) on my scanner.
 
One other thing to check, is for vacuum leaks. I know I have one around my Throttle Body. Also, the TB shaft has 2 o-rings on each side. I have replaced some. They get hard and chewed up. I also, lube up the bearings in there. Might check the flatness of the TB flange.
 
Well, more news to this. I compression tested the motor and it failed miserably. Pretty much all 6 cylinders were between 100 and 115 psi. The engine builder thinks that the cylinders washed which sounds plausible however since break in, i have not let it idle more than a few minutes.

I did verify my cam sensor prior to the compression test. I have checked with starting fluid for vacuum leaks. I changed my throttle body as well with no change.

Plain copper core plugs. The live data for the O2 is running between 0.7 and 0.9 with any of the 3 sensors I have had in there.

Fuel trim tends to be in the negatives. -3 to 4%

Smiley.png
 
600. From start up, ran at 2200 rpms for 30 minutes. After that, drove it all over creation. I live in the colorado mountains so it was a lot of up and down.
 
What type of piston rings? Moly or Cast iron? Also, did you run highway miles, and what RPMs? Did you vary the RPMs? What type of oil? Conventional, synthetic a breaking oil?
 
Did the builder provide a test sheet showing the compression when it was built?

The O2 sensor signal does suggest it's running rich.

Does the scanner show you're in Closed Loop once it's up to temp? What's the reported coolant temp? I assume you have a 195 deg thermostat.
 
What type of piston rings? Moly or Cast iron? Also, did you run highway miles, and what RPMs? Did you vary the RPMs? What type of oil? Conventional, synthetic a breaking oil?

I live in the mountains of colorado. The first 50 miles of so were around here, winding roads, some highway. I used 5w30 conv oil with a full bottle of zinc additive.
 
Did the builder provide a test sheet showing the compression when it was built?

The O2 sensor signal does suggest it's running rich.

Does the scanner show you're in Closed Loop once it's up to temp? What's the reported coolant temp? I assume you have a 195 deg thermostat.


It does show closed loop at operating temp. The coolant temp stays around 190 - 200.

Would low compression cause it to appear to be running rich?
 
What type of piston rings? Moly or Cast iron? Also, did you run highway miles, and what RPMs? Did you vary the RPMs? What type of oil? Conventional, synthetic a breaking oil?

Not sure on the type of rings but initially the O2 signal was pushing .9 to 1.2 and tripping the CEL and running open loop in the first 50 miles after that , it settled to the .7-.9 range. At that point i did drive it to work onthe highway 3 days in a row, 30 miles each way at around 2000 rpms. roughly 1200 feet decent/ascent.
 
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