O2 Sensor

I have a '96 Country with about 120k on the odo. I'm guessing that by the age and miles that it's about time for a new O2 sensor. It runs great, but I'm not impressed with the MPG. A few years ago, I put a new one on my '92, and saw the mileage grow from 15 to 20+. The '96 has OBD II, but the CEL is quiet. Should I wait for a code, or just go ahead and take a shot? Thanks

heyhar said:

I have a '96 Country with about 120k on the odo. I'm guessing that by the age and miles that it's about time for a new O2 sensor. It runs great, but I'm not impressed with the MPG. A few years ago, I put a new one on my '92, and saw the mileage grow from 15 to 20+. The '96 has OBD II, but the CEL is quiet. Should I wait for a code, or just go ahead and take a shot? Thanks

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What is the mileage? Any Mods to it, if so what are they? Manual, or Auto, 4.0 ???

No mods, bone stock, auto, almost 120k, predominantly Interstate driving, at the speed limit- heavily patrolled. The car runs excellent, recently tuned (no change), and it returns in the neighborhood of 15 MPG. My '92, 4.0, auto, bone stock, on a similar commute, will fetch 22-23 MPG. I know that the OBD I XJs had the 'Maint. Required' timer, which was 'cured' by removing the bulb. At about 130k, I replaced its O2 sensor with one bought at the dealer, and like I said, MPG jumped about 30%. I was hoping to hear that in fact the CEL in my '96 would not alert me to a malfunctioning O2 sensor, and that I would not be wasting my money replacing it. My only other experience with OBDII and O2 sensors was my '98 ZJ, where, even after replacing the sensor, the CEL would come back on, and you could feel a difference in performance, and see the mileage drop. I took to leaving the code scanner in the car, and canceling the light when it lit up every month or so, returning it to proper behavior. I have checked the '96 for any codes, but no light and no codes. Pardon my long- windedness, and thanks for your reply...Ray

There were some TSBs on the 96 Jeep 4.0s, one was a flash upgrade of the computer, the other a replacment of the Cat converter, both EPA mandated on Chrysler to do for free, but there have been complaints here that CELs turned up calling for new O2 sensors shortly after the computer flash, and one guys PCM died a week after the flash, his comments are in a thread I replied to here today. So based on your story, and the others here, I would avoid the stealership, and just get a new O2 sensor elsewhere and see what happens. Also, consider disconnecting the Battery for a minute, to force it (to clear the memory of the PCM) to relearn the new O2 sensor.

is there a good place to get O2 sensors online? (Looking for a 97 here)

Unfortunately, I had the opportunity to disconnect the battery last Friday- to replace it. It was at the garage for its annual fleecing by the state, and the mechanic asked me about the trick to starting it. It crapped the bed right in his service bay! So, it now has a new Interstate battery, not quite the Christmas present I was thinking of giving myself. I've had the car almost a year, and the battery was old, oh well...
Anyway, I understood the recall to be looking for cats with loose, broken innards, and mine doesn't rattle. My son's '95 cat does rattle, but no freebees for him! And, I'm not too keen on having the PCU meddled with, especially with reports of poorer performance and failure. So, I guess I'll bite the bullet and try a new O2 sensor, and hope it doesn't play hide and seek with the computer.......Ray

heyhar said:

Unfortunately, I had the opportunity to disconnect the battery last Friday- to replace it. It was at the garage for its annual fleecing by the state, and the mechanic asked me about the trick to starting it. It crapped the bed right in his service bay! So, it now has a new Interstate battery, not quite the Christmas present I was thinking of giving myself. I've had the car almost a year, and the battery was old, oh well...
Anyway, I understood the recall to be looking for cats with loose, broken innards, and mine doesn't rattle. My son's '95 cat does rattle, but no freebees for him! And, I'm not too keen on having the PCU meddled with, especially with reports of poorer performance and failure. So, I guess I'll bite the bullet and try a new O2 sensor, and hope it doesn't play hide and seek with the computer.......Ray

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Hide and seek is not the problem, the computers create sensor data tables over time that they use in their calculations, algorithyms they use for engine timing and fuel control, and disconnecting the battery clears the memory of those tables and forces the computer to make new tables from the current, new sensors.

I have never bought O2 sensors online, but nearly everyone has them including Autozone. I got decent prices and local inventory pick up from Autozone for mine, and they carry Bosch O2 sensors. Get the OEM style with the O2 bheater and the OEM style plug, do not buy a generic O2 sensor.