Notices
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here XJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Sponsored by:
Sponsored by:

Replacing O2 sensors. Which is which?

Old 02-13-2019, 01:00 PM
  #1  
Newbie
Thread Starter
 
Flock2Tribe's Avatar
 
Join Date: Feb 2018
Location: Philadelphia
Posts: 10
Year: 1996
Model: Cherokee(XJ)
Engine: 4.0
Default Replacing O2 sensors. Which is which?

I have decided that it may be a good idea to replace my O2 sensors. Poor mileage, hard to start in cold, runs different based on weather, hard to start when engine is hot, PO told me to do it. Tons of reasons. I just now realized that there is an upstream and downstream O2 sensor. I only knew about the one near the catalytic converter. Do they both have the same function? Should they be replaced at the same time?

This is 96 XJ with 287K

Thanks in advance.
Flock2Tribe is offline  
Old 02-13-2019, 01:21 PM
  #2  
CF Veteran
 
00t444e's Avatar
 
Join Date: Nov 2015
Location: Southern OH
Posts: 1,815
Year: 1997
Model: Cherokee(XJ)
Engine: 4.0
Default

The upstream o2 sensor that's before your converter is the one that affects performance, the downstream after the converter is only there to trip a code if the cat isn't working right.
00t444e is offline  
Old 02-13-2019, 01:27 PM
  #3  
CF Veteran
 
jordan96xj's Avatar
 
Join Date: Dec 2015
Location: Syracuse, NY
Posts: 1,777
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
Default

On a 96, the one involved with air/fuel mixture adjustments (via the PCM) is the upstream sensor. If you only replace one, make it the upstream sensor. The downstream is used to measure catalyst efficiency (emissions standards).

Almost any symptom that can be caused by an o2 sensor, can also be caused by a bad MAP sensor (on the throttle body). O2 sensors are typically not involved with poor cold-starts. As they take 60-120 seconds to even be used by the computer after a cold start.

Do you have an OBD2 scanner? they are invaluable for seeing what your computer is doing, and how it is adjusting the air/fuel ratio, and what it thinks the O2 sensors are doing. They can be had for about $25 these days on amazon (I use the BAFX Bluetooth OBD2 scanner for Android for my 96).
jordan96xj is offline  
Old 02-13-2019, 06:29 PM
  #4  
Member
 
nickfancher1's Avatar
 
Join Date: Aug 2014
Location: Phoenix, AZ
Posts: 122
Year: 1996
Model: Cherokee
Engine: 4.0L
Default

Only buy NTK O2 sensors (they’re the OE maker).

I had bought Denso O2 sensors and they failed after a week or so, it ran bad and set a check engine light. I had replaced the originals just for the heck of it.

I bought the proper NTK’s and it runs perfect.

Just a warning. 96’ is a bit of a bastard year. For mine, I had to buy sensors for a 97’ because 97’ sensors had a different electrical plug.

and my Jeep isn’t even hacked or cobbled together.
nickfancher1 is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
bzauche
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
5
06-08-2012 12:24 PM
rtralabama
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
4
08-11-2011 08:35 PM
b_heier.4X4
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
7
02-11-2011 01:37 PM
Soldat
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
21
01-11-2010 05:06 PM

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 

Thread Tools
Search this Thread
Quick Reply: Replacing O2 sensors. Which is which?


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description: