Upstream O2 Sensor Shenanigans
 

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So after having a new to me '97 XJ on the road for a little over a month, I've noticed that the MPG is terrible. I wasn't expecting good MPG to begin with on a 3 inch lift and 31s, but I'm averaging about 10 MPG. That seemed horrible so I did some investigating and found that the cats had been removed and I only have an upstream O2 and that the wires had been cut. My question: the 4 wires on the top of the motor, are they the wires that go to the 02? Do I need to get a pigtail for the harness? Photos for reference.

Pretty sure they are the wires. My 95 only has an upstream sensor and IIRC that's exactly where the wires run.

I would get a pigtail for the O2 sensor - otherwise you have to cut wires every time you change an O2 sensor. You should be able to fix/replace the upstream sensor and see a nice improvement in MPG.

Gotta love some of these P.O.'s... ugh.. :\

I don't think those are the wires. You should see a harness that points in the direction of the sensor.

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PatHenry you don't know the half of the Jerry rigging and electrical gremlins I've come across so far. For example, they put an after market radio in with electrical tape and wire nuts. WIRE NUTS! :brickwall: I've spent more time behind a multi-meter this past month than I would have cared to.

XJ, are you sure? I found this diagram that matches the wires I have coming from the top of the motor. Still don't understand why they cut off the harness connector.

On my 97 those are the upstream o2 sensor wires. https://cimg9.ibsrv.net/gimg/www.che...d6fba8444e.jpg
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Note from DJ
More information https://cimg7.ibsrv.net/gimg/www.che...64590fbe82.png

Where is the connector? Did 97 just straight wire the O2 sensor in?

On my 95 the wiring runs the same way (it's sort of tucked through one of the PS brackets to keep it away from the spinning belt and hot exhaust) and there's a little (flimsy) bracket that the plug pops into using a plastic trim-panel-style clip (it looks like a short, fat screw).

Yes there is a connector I just didn't get it in the pictures.

Update:
So after a trip to the local junk yard and a lot of research I ended up sourcing a pigtail from a 1999 Grand Cherokee Laredo and soldering it in to the existing wiring. Already noticing better performance and MPG with the O2 sensor installed. Now I just have to figure out what I'm going to do with the downstream since the PO deleted the Cat. Might just run a MIL eliminator on the downstream plug until I can raise the funds for a new cat. Thanks to everyone who took the time to reply, the struggle continues!

The downstream sensor has no affect on performance so you don't have to do anything with it, unless the check engine light bothers you, then you can just pull the bulb.

[QUOTE=Mobius2;3503856] poops wrong picture.. but you know the dent I speak of, yes??https://cimg2.ibsrv.net/gimg/www.che...7b571bdf44.jpg
how did you get that dent in your down pipe?

[QUOTE=Sloerolla;3506463]It comes that way from the factory.