Yj 1990 jeep wrangler o2 sensor.... need to down grade the fumes!

Amy lee

New Member
Joined
Aug 26, 2021
Messages
3
Location
Nola
I am a new jeep owner. Just bought a 1990 jeep and have so far been towed twice and then off to a muffler shop. All is suppose to be perfect on it now except i am noticing i am inhaling lots of exhaust. Didn't seem to do that before. Muffler guy said he fixed holes and added a new muffler and that i am just picking up exhaust from it running with the top down. It has no ac so i plan on always having the top down. I googled and asked him about the o2 sensor? Maybe it went bad and i need to replace it. He says if so the check engine light would come on and i would hear it making noise. The more i google the more i am finding there is no check engine light on the 1990s. How hard is this job and can i change it myself? I like having a machanic that will help me keep this thing running but i am kinda interested in doing pthings if capable. Any suggestions on part to use? Looks like the one on there is a single wire with no heat? I will post some pics.... any help and advice is appreciated. Thanks

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jeepjoe43

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Dec 4, 2020
Messages
926
Location
Black Canyon City, AZ 85324
That is the clutch slave cylinder bleeder valve. You're good.

As to the O2 sensor, I'm guessing it's throttle body FI as the sensor is in the manifold.
Mine is a '91 with MPI and I put my sensor where yours is (mines supposed to be in the head pipe about 4" from there).
The only reason I did this was the new exhaust had the bung but they didn't drill the pipe and I knew the manifold had a plug.
What difference could 4" make, well I've got similar issues to yours now and it's developed a random miss.
Maybe related, maybe not, dunno.
But, if I don't warm it up first, I'll get CE light and code 52 every time, O2 rich.

As for yours, I'm thinking the sensor is fouled.
Coolant from a leaking head gasket will do it, Oil will too.
As will a sticky injector or leaded fuel.
The fouling on the sensor will look different for each.
 
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Amy lee

Amy lee

New Member
Joined
Aug 26, 2021
Messages
3
Location
Nola
That is the clutch slave cylinder bleeder valve. You're good.

As to the O2 sensor, I'm guessing it's throttle body FI as the sensor is in the manifold.
Mine is a '91 with MPI and I put my sensor where yours is (mines supposed to be in the head pipe about 4" from there).
The only reason I did this was the new exhaust had the bung but they didn't drill the pipe and I knew the manifold had a plug.
What difference could 4" make, well I've got similar issues to yours now and it's developed a random miss.
Maybe related, maybe not, dunno.
But, if I don't warm it up first, I'll get CE light and code 52 every time, O2 rich.

As for yours, I'm thinking the sensor is fouled.
Coolant from a leaking head gasket will do it, Oil will too.
As will a sticky injector or leaded fuel.
The fouling on the sensor will look different for each.
Wow... thank you! That link explains everything. I think i will give it a go. I don't think the 1990 jeep has a way to check codes so maybe i will just change it and see what happens.
 

jeepjoe43

YJ Enthusiast
Lifetime Supporting Member
Joined
Dec 4, 2020
Messages
926
Location
Black Canyon City, AZ 85324
Wow... thank you! That link explains everything. I think i will give it a go. I don't think the 1990 jeep has a way to check codes so maybe i will just change it and see what happens.
It should have OBD1.
You can check for codes as follows;
Without starting the engine, Ignition on, off, on, off, on, then the Check Engine Light will flash in a series, those are the codes.
This is if the CEL is actually working, it should come on when you first turn on the ignition before starting it.
There is also a plug for a code reader on the firewall by the brake booster.
 

Gilaguy23

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Apr 12, 2021
Messages
669
Location
Q town New Mexico
Ha, for us hard learners ;0 the code patterns can be a bugger to get right of you have several. The 02 sensor is a piece of cake to replace and cost around $35 or so. Lots of guys say do NOT use Bosch ones but NKT which is NGK's line or a another common brand. far as the fumes, my 91 has a clean bill of health but it is a bit stinky with the back window off or rolled up. Thus I never run like that anymore. I run the top with no doors or sides and have added a 90 out the side or rear corner instead of straight out the back. It did help some with the fumes.