Oxygen Sensor

[1991LS400]

Hey guys,

What exactly does the Oxygen Sensor (O2 sensor) do for my 1991 LS 400? If it needs changing, how would I know?

P.S. Would anyone happen to know the part number of the O2 sensor for a 91 LS 400?

[blake918]

You would know usually by a check engine light. Also, if your car starts to feel sluggish and/or is getting bad gas mileage, it might be time for new ones. I believe the 02's maintain the air-fuel ratio...not 100% sure though.

[Lexls]

Yup, the O2 sensors monitor the fuel/air ratio. Usually you do get a check engine light if one goes out. However, this doesn't always happen. I had no check engine light but my main O2 sensors were out of spec......still working though. See my site for more info.

Replacing all 4 sensors DID help bring my MPG back to normal range. They should be changed every 60K or so I believe, most people don't and they get a check engine light.

[1991LS400]

Yup, the O2 sensors monitor the fuel/air ratio.  Usually you do get a check engine light if one goes out.  However, this doesn't always happen.  I had no check engine light but my main O2 sensors were out of spec......still working though.  See my site for more info.

Replacing all 4 sensors DID help bring my MPG back to normal range.  They should be changed every 60K or so I believe, most people don't and they get a check engine light.

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There are 4 Oxygen sensors for the 1991 LS 400's? Would you or anyone else here on LOC happen to know the part #'s for the 4 sensors? Are they all the same part #, I just need 4 of them or something? PLEASE HELP! Someone's selling an O2 sensor BRAND NEW for $30 and I'm wondering if I should purchase it but I need the part number.

P.S. Can I replace the 4 Oxygen sensors myself?

[Econ]

Yeah, you can replace them yourself - lexls.com has a rockin' walkthrough, you definitely need to review it before replacing the sensors. Get an O2 sensor wrench if you can spare the $, they make things a little easier in my opinion (I got a set of 3 for $25 from the site lexls.com refers you to for sensors).

Part #s for the O2 sensors:

Front - 8946550010

Rear - 8946550020

Torque specs are 33 ft. lbs.

[ylekiot1]

I got universal sensors from oxygensensors.com and soldered the connectors from the old ones to the new ones. They also sell the ones with the connectors but for alot more $.