`97 XJ upstream O2 sensor problems - JeepForum.com
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Unread 07-04-2009, 03:32 PM   #1
my7sundays
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`97 XJ upstream O2 sensor problems

I have a `97 Cerokee Country. I have had 3 forward O2 sensors go in the past three months. The latest one only lasted a week. The previous one lasted a little over 2 weeks. I just changed the cat converter with the last one. I am getting frustrated to say the least. Any suggestions? The loss of gas mileage alone is enough to kill the wallet!

Charlie

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Unread 07-04-2009, 03:39 PM   #2
StaleAle
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Quote:
Originally Posted by my7sundays View Post
I have a `97 Cerokee Country. I have had 3 forward O2 sensors go in the past three months. The latest one only lasted a week. The previous one lasted a little over 2 weeks. I just changed the cat converter with the last one. I am getting frustrated to say the least. Any suggestions? The loss of gas mileage alone is enough to kill the wallet!

Charlie
Is your Jeep running rich or something? Are they covered in crud when you removed them?
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Unread 07-04-2009, 04:00 PM   #3
my7sundays
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I had it hooked into a friends Snap-On device, and it said the upstream was running lean. That was before I replaced the first one that went bad. The second one I replaced just went on me today. There was a little oil and dirt on the original one, and the second one also had a little fluid on it. I found that I have a slight leak in my power stearing system somewhere, and it looks like that is what was on the sensor connection. Could that be the culprit?
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Unread 07-04-2009, 04:02 PM   #4
my7sundays
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I am talking about the connectors, when I mention of the oil and dirt. The actual sensors were just covered in black soot, and dry.
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Unread 07-04-2009, 04:03 PM   #5
SILASPRIT
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what was on the part of the sensor that stuck into the flow ox exhaust? was there buildup? was it wet?
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Unread 07-04-2009, 05:41 PM   #6
Ed Rico
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How's the condition of your exhaust system? Any cracks, etc in the exhaust before the upstream O2 sensor can allow outside air into the exhaust stream, fool the PCM into thinking you're running lean, and improperly richen the A/F mixture.

-Ed Rico
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Unread 07-06-2009, 05:37 AM   #7
my7sundays
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The exhaust system is quite tight. No leaks before the upstream sensor, and the rest of the system is new. Anyway, I decided to unplug both sensors and see what happens. Well....to my surprise, the performance level went up, and my gas mileage is better than ever, pushing near 26 mpg on the highway at 55mph. Of course the check engine light is on, but I can live with that until my next inspection. I`ll throw in a new upstream sensor and plug them both in for the inspection, and then unplug them when I get home.

My conclusion so far.........emissions is a rip-off to the auto owner. Hey.....why does my friend with the new Harley Davidson get to run almost straight pipes on his bike, and never have a problem getting inspected?

Thanks everyone for the input. I`m always open for more.
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Unread 07-06-2009, 06:06 AM   #8
Ed Rico
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Not sure how inspection works where you are in NY; here in IL it's not enough to have the MIL off, all '96-up OBD-II vehicles are checked by plugging in the diagnostic port to check for system ready status as well as codes (i.e. you can't just reset the battery outside the test center) so you might not be out of the woods on this one. Regardless of MIL status, without a functioning upstream O2 sensor, you're always running open loop - it may run better than you're experiencing now but will ultimately take out your new cat due to dumping excess fuel into the exhaust stream. If you have access to a device that can do more than just read codes, I think you'd be better served by attempting to run down why you're getting an improper signal at the upstream O2 sensor. OBD-II problems can be frustrating to diagnose (if you search, you can read about the problem on my '97 XJ with a bad ground taking out the O2 sensor heater circuit), but overall the system does a good job when working as intended.

Best of luck,

-Ed Rico
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Unread 07-06-2009, 10:07 AM   #9
SILASPRIT
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Just so you know with a fuel injected engine o2 sensors aren't just for emmissions, they are actually a crucial part to the engine constantly giving the computer the proper air-fuel ratio... I don't see how it's running so well with them unhooked but there is a great chance you can be damaging parts of your engine.... Too much fuel= cylinder wash Wich actually washes the oil off of the cylinder walls and will cut out the walls resulining in bad to no compression. Or not enough fuel can cause you to actually heat things up so much it can burn holes in your pistons. I bet it is going in and out of open/closed loop at an idle huh?(rpms will drop/rise every few seconds) my recomendation is to get both new o2 sensors and then clean your tb. If they still go out take them back on warranty..... Most jeeps have heated o2 sensors because it is not a conventional cast exhaust manifold... It is a tube style which is a lot cooler than the cast style... This means that a regular o2 will run too cold and not properly.. The heated o2 is run in many cars with aftermarket headers for the same reason... Heat. Find out which of the (3 wires I think) going to the o2 is just a 12v power source. That's the wire for the heating element in the o2. If it isn't reading power then there might be something wrong with your wiring.
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-SOLD-
1997 Grand Cherokee 5.2 Limited - D44a Trussed 4.10 Gears - HP30 4.10 Gears - NP242 - IRO HnT - IRO Custom Drive Shaft - 4.5" lift - JKS Quicker Disconnects -
RC Front ADJ. Trackbar - IRO Rear ADJ. Trackbar - Rusty's Lower ADJ. CA's - Front tow hooks - Rear OE Hitch - T-Case Skid -
Gas Tank Skid - Bilstein 5125's - 31" MTR's - Magnaflow SS Muffler - 1.25" Wheel Spacers - Custom Rock Sliders - Cobra 19 DXIV


I am an Authorized IRO dealer!!
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Unread 07-06-2009, 05:50 PM   #10
my7sundays
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I knew it was too good to be true. I actually made an appointment with my mechanic to give it a good look over. He`s never failed me in the past with any of my other vehicle problems. Thanks very much for the detailed info everyone. I will pass it on to my friend at the shop. I`d rather get it fixed the right way. By the way....it idles fine, with no RPM change.

It sure was nice to think the Jeep Gods had performed a miracle for me though!! I should have stuck with old CJ`s, like I always had in the past.
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Unread 07-06-2009, 06:11 PM   #11
my7sundays
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no sensors...no problem

I am currently still running with both sensors unplugged, and the Jeep has never run better. There is no surging, the idle is not fluctuating at all (because of open loop), there is no carbon blowing out of the exhaust, and I have been checking the plugs once a week (as suggested by a mechanic friend) and finding them to be just as they should look. If it were running too lean, I`m told the plugs would burn up before the pistons did. I am also getting a few miles more to the gallon. Apparently, the computer has adjusted itself to run the the engine without the sensors. Has anyone else experienced this?

I`ll still have the problem looked into as soon as I can go without the Jeep for a few days.

Last edited by my7sundays; 07-19-2009 at 06:02 PM.. Reason: just an update
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