NAXJA Forums -::- North American XJ Association  

Go Back   NAXJA Forums -::- North American XJ Association > NAXJA's Technical Forums > OEM Tech Discussion
Register FAQ Users List Calendar Mark Forums Read
HOME Member FAQ Sponsor Info Rules Donate Bylaws Store Members Chat E-Mail

OEM Tech Discussion Forum for OEM (Original Equipment) or stock XJs and MJs.

Reply
 
Thread Tools Display Modes
  #1  
Old February 26th, 2007, 14:52
xylonjay's Avatar
xylonjay xylonjay is offline
NAXJA Forum User
 
Join Date: Dec 2006
Location: Minneapolis,MN
Posts: 71
What are the symptoms of a bad 02 Sensor?

I cant find anything in the forums that explains what the symptoms of a bad 02 sensor are. My 94 XJ with 207,000 miles is hesitating randomly, most times it hesitates at freeway cruising speed, and sometimes if you are taking off from a stop light. Im stumped. Any help would really be awesome.
Reply With Quote
  #2  
Old February 26th, 2007, 16:00
Ecomike's Avatar
Ecomike Ecomike is offline
NAXJA# 2091
 
Join Date: Dec 2006
Location: Texas
Posts: 14,367
Re: What are the symptoms of a bad 02 Sensor?

Quote:
Originally Posted by xylonjay
I cant find anything in the forums that explains what the symptoms of a bad 02 sensor are. My 94 XJ with 207,000 miles is hesitating randomly, most times it hesitates at freeway cruising speed, and sometimes if you are taking off from a stop light. Im stumped. Any help would really be awesome.
Just unplug the O2 sensor and drive it. If the hesitation stops it is, was the O2 sensor. Bad O2 sensors kill the gas mileage big time!!!! That is the biggest clue that they are toast.

Hesitation is frequently caused by a bad TPS sensor. Search "Throttle Position Sensor testing" here for more details. Also check into the EGR valve (I think 94's still had EGR valves). Search Exhaust Gas Recirculation or EGR* (Three letter search words like EGR do not work here).
Reply With Quote
  #3  
Old February 26th, 2007, 17:18
Tom R. Tom R. is offline
NAXJA Member #30
 
Join Date: Jun 2002
Location: Utah
Posts: 2,201
Re: What are the symptoms of a bad 02 Sensor?

EGR valves went out with the non-HO motors......thankfully!
Reply With Quote
  #4  
Old February 26th, 2007, 17:37
xylonjay's Avatar
xylonjay xylonjay is offline
NAXJA Forum User
 
Join Date: Dec 2006
Location: Minneapolis,MN
Posts: 71
Re: What are the symptoms of a bad 02 Sensor?

Thanks, I will try and locate the 02 sensor and disconnect it, also, whereabouts is the the TPS? Is that under the hood, or under the truck?
Reply With Quote
  #5  
Old February 26th, 2007, 18:39
89xjgrey's Avatar
89xjgrey 89xjgrey is offline
NAXJA Forum User
 
Join Date: Jan 2004
Location: Columbus, Ohio
Posts: 324
Re: What are the symptoms of a bad 02 Sensor?

A bad o2 sensor will not necessarilly cause a hesitation, but it will cause you to run rich, or lean depending on how it's reading. Earlier xj's only use one oxygen sensor to monitor emissions and adjust fuel trim. With access to a scanner with 'live data' capabilities, you can monitor the o2 sensor volts and make sure it's switching properly, but a lazy o2 sensor will definately cause poor fuel economy. The TPS, is located right at the throttle body, and I really don't recomment d/c the o2 sensor...just my .02
Reply With Quote
  #6  
Old February 26th, 2007, 19:01
xylonjay's Avatar
xylonjay xylonjay is offline
NAXJA Forum User
 
Join Date: Dec 2006
Location: Minneapolis,MN
Posts: 71
Re: What are the symptoms of a bad 02 Sensor?

Thanks 89xjgrey, I'll take your .02 the reason being im is im still getting the same mileage right now, and someone else had mentioned the TPS, but I dont have much experience troubleshooting sensors, so I am gonna have the TPS checked out at my buddys shop. I should mention I have the 5-speed manual. Would that make any difference?
Reply With Quote
  #7  
Old February 26th, 2007, 21:46
Ecomike's Avatar
Ecomike Ecomike is offline
NAXJA# 2091
 
Join Date: Dec 2006
Location: Texas
Posts: 14,367
Re: What are the symptoms of a bad 02 Sensor?

Quote:
Originally Posted by 89xjgrey
A bad o2 sensor will not necessarilly cause a hesitation, but it will cause you to run rich, or lean depending on how it's reading. Earlier xj's only use one oxygen sensor to monitor emissions and adjust fuel trim. With access to a scanner with 'live data' capabilities, you can monitor the o2 sensor volts and make sure it's switching properly, but a lazy o2 sensor will definately cause poor fuel economy. The TPS, is located right at the throttle body, and I really don't recomment d/c the o2 sensor...just my .02
The proposed O2 disconnection was only offered as a short troubleshooting test since he seemed to think it was the O2 sensor causing his hesitation. It was not proposed as a permanent fix.

I know from my own tests that these jeeps (at least the older Renix jeeps) run fine with out an O2 sensor, but who can afford the gas! They seem to use twice as much gas (they run rich, open loop mode, at least the Renix ones do) when the O2 sensor goes bad or is disconnected.
Not sure about the O2 sensors disconnection effect on the later OBD-1 models and his is a 94, OBD-1 model.

TPS is definately the "Usual Suspect".

Yes, the 5 speed manual does have a TPS, but it has only one 3 pin connector. The Automatics have an extra connector on the TPS that goes to the auto-tranny.

He should probably take it to someplace like Autozone to get a free scan since his has the OBD-1 scan capability!
Reply With Quote
  #8  
Old February 27th, 2007, 08:45
xylonjay's Avatar
xylonjay xylonjay is offline
NAXJA Forum User
 
Join Date: Dec 2006
Location: Minneapolis,MN
Posts: 71
Re: What are the symptoms of a bad 02 Sensor?

Ecomike, they are able to test these at Autozone? I didnt know that. Do you know how much do they charge to scan? Will it find other issues as well? I apologize for all the questions. Im thankful for all the input sofar
Reply With Quote
  #9  
Old February 27th, 2007, 08:48
Rick Anderson Rick Anderson is offline
NAXJA Forum User
 
Join Date: Jan 2006
Location: Lusby, MD
Posts: 1,197
Re: What are the symptoms of a bad 02 Sensor?

I "believe" the '94 XJ had the Chrysler Engine controls, this will show you any fault codes stored by the engine computer, a bad O2 sensor being one of them.

When I say turn the key "on", I mean turn it to the run position, NOT the starter position and actual start the motor.

Turn the Key On-Off-On-Off-On within 5 seconds. Watch the "Check Engine Light" and count the flashes. It will pause between numbers, meaning a new number is coming. Arrange the numbers in 2 digits codes as they are flashed out.

Code 21 is usually for bad O2 sensor on Chrysler Vehicles.

Ignition is often a cause for hesitation as well. Not only fresh spark plugs, but the ignition wires themselves breakdown and leak the super high voltage, as well the cap and rotor needs periodic replacement. Cap/Rotor and Spark Plug wires should be replaced every 66k miles, if it hasn't been done since 141k miles on the vehicle, I would try that.
Reply With Quote
  #10  
Old February 27th, 2007, 08:53
j99xj's Avatar
j99xj j99xj is offline
NAXJA Forum User
 
Join Date: Jul 2006
Location: Colorado Springs, CO, USA
Posts: 800
Re: What are the symptoms of a bad 02 Sensor?

I had random hesitations/stalling issues when my 02 was on the fritz.

At low rpm and throttle positions the engine would lose all of its low rpm torque (almost like someone suddenly put on the parking brake half way) then the engine would backfire a few times and then the torque would instantly come back throwing me back in my seat.

New Bosch 02 sensor, no problems since.
Reply With Quote
  #11  
Old February 27th, 2007, 09:49
xylonjay's Avatar
xylonjay xylonjay is offline
NAXJA Forum User
 
Join Date: Dec 2006
Location: Minneapolis,MN
Posts: 71
Re: What are the symptoms of a bad 02 Sensor?

Looks like cap, plus and wires all replaced recently. Ive owned the Jeep since November, and have no maintence records showing what has/hasnt been done. I do know the previous owner took meticulous care of it, and in my opinion the plugs, wires, cap all look to have been replaced within the last year or so. Im not sure about the sensors though. After work im gonna drive straightb to Autozone right by my house and have em check it out for me. Is the TPS sensor hard to replace (im an XJ newbie mind you)?
Reply With Quote
  #12  
Old February 27th, 2007, 13:11
ren's Avatar
ren ren is offline
NAXJA Forum User
 
Join Date: Dec 2004
Location: frenchburg, ky
Posts: 1,196
Re: What are the symptoms of a bad 02 Sensor?

TPS hard to replace? No, just mildly annoying to "set" corectly for the needed readings. You need a digital multi-meter to set the thing. Try searching for TPS replacement, to learn how to set it. Also, get a good service manual, as it will work wonders for you and the XJ.
Reply With Quote
  #13  
Old February 27th, 2007, 13:24
xylonjay's Avatar
xylonjay xylonjay is offline
NAXJA Forum User
 
Join Date: Dec 2006
Location: Minneapolis,MN
Posts: 71
Re: What are the symptoms of a bad 02 Sensor?

Well, took the XJ to Autozone and they said they only scan cars newer than '96 they had only a ODB2 scanner. I then took it to checker and they let me use theirs and it said there were no codes, or data. Soo, im thinkin fuel pump, or filter now......? Thanks
Reply With Quote
  #14  
Old February 27th, 2007, 13:30
UNCC_99XJ's Avatar
UNCC_99XJ UNCC_99XJ is offline
Twisted Up
 
Join Date: Jan 2005
Location: Concord, NC
Posts: 8,747
Re: What are the symptoms of a bad 02 Sensor?

Follow the key on-off method mentioned above and see if you can get the code yourself.

On the o2 sensor causing a rich/lean topic, the upstream o2 sensor is used to control air/fuel mixture and will make you run rich/lean if it goes bad. The downstream o2 sensor (the one after the CAT) is used only to monitor the cat. converter and make sure it's doing its job and doing it properly. The reason I say this is a lot of people get these two confused, or think that the downstream o2 also controls air/fuel mixture and will replace it in an attempt to boost milage or solve a problem.
__________________
-Timbo - SEC Treasurer
-'99 Sport, RE 4.5" and a few other things
-'13 Performance Blue Ford Focus ST. DD & Race Car.
Reply With Quote
  #15  
Old February 27th, 2007, 13:48
Rick Anderson Rick Anderson is offline
NAXJA Forum User
 
Join Date: Jan 2006
Location: Lusby, MD
Posts: 1,197
Re: What are the symptoms of a bad 02 Sensor?

I don't think a '94 will have a downstream O2 sensor. My '95 2.5L 4cyl does NOT. OBDII was mandated in '96 model year, and the requirement to test the Catalytic Converter for Proper Function brought on the Upstream/Downstream O2 sensors to compare In/Out of the CAT.

But there were pre-1996 vehicles that did NOT have 2 O2 sensors, and it could be different between 6cyl and 4cyl.

So, if you do have 2 O2 sensors, remember, the O2 sensor between the engine and the CAT is the Upstream, it is used to measure the A/F ratio for the engine computer. The Downstream O2 sensor is after the CAT and is only there to check if the CAT is working correctly, it does NOT effect how the motor runs at all.
Reply With Quote
Reply


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

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
symptoms of bad steering box? snow drifter OEM Tech Discussion 6 December 14th, 2006 00:36
Symptoms of a bad cat? JeepMaz OEM Tech Discussion 9 September 30th, 2006 10:22
Bird Flu Symptoms churky89 Non-Tech / Off Topic 5 November 12th, 2005 16:55
Here's the symptoms..FIRE... what is the cause? Twisted XJ OEM Tech Discussion 3 November 5th, 2005 19:31
??? CPS Symptoms ??? gptherezonlyone Modified Tech Discussion 3 November 15th, 2003 12:22


All times are GMT -7. The time now is 23:09.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014