Need help finding upstream 02 sensor on '99 TJ?

[Moab]

So apparently the '99 only has one upstream and one downstream 02 sensor. I'm having trouble locating the upstream sensor on my Jeep. And the part number to replace it with.

Here's what appears to be the upstream sensor in the below two pics. (We also located the downstream sensor that plugs into the actual header not the manifold. So we're pretty sure we've got the right upstream 02 sensor located. But I think I ordered the wrong part. See below.):

This sensor looks nothing like the part number I ordered NTK 23151 below:

Can anyone confirm that that is the upstream sensor in my first two pics? And what part number I need to replace that? Or am I not looking at the right sensor to begin with?

 

[Lou]

That is the intake manifold not the exhaust manifold. The exhaust manifold is under the intake manifold.


You are looking at not only the wrong sensor, but the wrong manifold.

 

[Moab]

That is the intake manifold not the exhaust manifold. The exhaust manifold is under the intake manifold.


You are looking at not only the wrong sensor, but the wrong manifold.

Thank you. Should I be able to see it from under the Jeep then?

 

[Moab]

Here's a pic of what I believe to be the downstream sensor. The upstream must be forward and up from that sensor. Correct?

 

[Lou]

Thats the upstream. Upstream is before the cat, downstream is after the cat. Locate your cat and look beyond that for the downstream.

 

[Jerry Bransford]

Thats the upstream. Upstream is before the cat, downstream is after the cat. Locate your cat and look beyond that for the downstream.

Exactly, you have a great photo of your upstream sensor. As said, your downstream O2 sensor is mounted on the catalytic converter. Upstream vs. downstream refers to being before the catalytic converter(s) or after it/them.

 

[Moab]

F%$&! Thank you so much. (Slowly pulling my head out of my ass...)

 

[Moab]

Exactly, you have a great photo of your upstream sensor. As said, your downstream O2 sensor is mounted on the catalytic converter. Upstream vs. downstream refers to being before the catalytic converter(s) or after it/them.

I was getting confused from that diagram from the 02 sensor thread. Thank you both for the help. AT least I know where it's at now. And have the right part.

 

[Moab]

Well the O2 sensor came out and went in without a hitch. As did the tune up. I ran errands today and instead of the normal 1/8th of a tank. I used a needle of gas. Very very happy with the results.

 

[Lou]

How many miles were you getting to how many gallons? I’m lucky to get 200 miles to 16 gallons.

 

[Moab]

How many miles were you getting to how many gallons? I’m lucky to get 200 miles to 16 gallons.

I didn't have it calculated. All I know is I was spending $20 every time I drove my kid to Santa Monica from El Segundo. About 10-15 miles each way. It was bad. IT wasn't running rough. I just did the tune up cause I had the stuff. I think it was the O2 sensor that improved it.