TJ running rich - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ General Discussion Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 01-21-2013, 08:03 AM   #1
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
TJ running rich

Newb to my TJ, and I think it's running a little rich. I am guessing that based on smell and the fact that I get 10 mpg if I am lucky. (I bought this Jeep knowing I would probably have to take out second mortgage on fuel for it, but based on what I have seen here, 8-10 mpg is kinda bad, even for a Jeep). I have a 97 TJ 2.5l 5-spd sitting on 31s with a 3" lift and stock gearing. Enging is throwing O2 sensor codes, and I have new ones on order. Also, I run 93 octane gas and the occasional shot of Lucas fuel system cleaner through it.

Is there anything else that would be causing this? Will replacing the 02 sensors cure the problem, or are there other things I should be doing as well? I do have new wires, plugs, cap, roto, air filter, etc going in tomorrow as well. Figured since I was tearing into the O2 sensors, I might as well do a full tune up since I have no idea how old that stuff is.

Any help and suggestions are appreciated!!

__________________
ranger44 is offline   Quote Quick Reply
Old 01-21-2013, 10:31 AM   #2
Jeeper
 
jgorm's Avatar
 
Join Date: May 2010
Location: San Diego
Posts: 1,918
Stop running 93 and switch to 87. No need for lucas cleaner. The O2s can be the problem. Once you install the new mopar part numbers then see if the code goes away.

__________________
my 06 LJ rubicon
2.5" SL, 1" BL, DIY highline, 35s with double beadlocks.
jgorm is offline   Quote Quick Reply
Old 01-21-2013, 10:48 AM   #3
Jeeper
 
Dextreme's Avatar
 
Join Date: Oct 2011
Location: Oregon City, OR
Posts: 3,661
Images: 1
Yep, I bet you will see a big difference with new O2 sensors. And Jgorm is right...use 87 octane. It will produce the most/optimal power for your 2.5L motor.
__________________
'99 Chilli Pepper TJ Wrangler "Mistress"
33x12.5 DuraTracs
Zone 4.25"
Dextreme is offline   Quote Quick Reply
Old 01-21-2013, 04:47 PM   #4
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
Pardon my ignorance, but if i don't get an error code, could an O2 sensor still be bad? Atm I'm pretty much in the same boat mpg wise, maybe a bit better. Running 31s with no lift, d44 3.73 gear ratio and d30 at the front. 4.0 manual 5sp. 2001 with no mods and as light as i can make it. Any input would be welcomed. Recent oil change but my mechanic said there was no need to change tranny oil.
RevCo666 is offline   Quote Quick Reply
Old 01-21-2013, 06:22 PM   #5
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
It is possible. Depends on where all your Jeep came from. I have heard horror stories of used car lots and private sellers cutting or unscrewing the CE light so you don't know. If you actually put a code reader on it and you aren't getting a code, then that I am not sure about.

After we get through this sub-zero blast of cold weather in the next few days, I will tear into the tune up process and let yall know if it helped.
__________________
ranger44 is offline   Quote Quick Reply
Old 01-21-2013, 06:53 PM   #6
Jeeper
 
Join Date: Oct 2011
Posts: 1,606
Quote:
Originally Posted by RevCo666 View Post
Pardon my ignorance, but if i don't get an error code, could an O2 sensor still be bad?
Oxygen sensors degrade as a function of time in service. There is a wide range of efficiency between "Perfect" and "Bad."
tangofox007 is offline   Quote Quick Reply
Old 01-21-2013, 09:29 PM   #7
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
Quote:
Originally Posted by tangofox007 View Post
Oxygen sensors degrade as a function of time in service. There is a wide range of efficiency between "Perfect" and "Bad."
Would it be a waste of time to just change them anyways? I've done the plugs when i fist got the jeep this summer, two oil changes since i do more stop and goes. The k&n filter is fresh out of the box/oiled from the factory also from the start... I knew jeeps are little pigs and its winter but I know something might be a foot lol

My last truck, mazda b3000 when i bought it from a used car lot had issues right away with O2 sensor(check engine light was the give away plus using obd reader helped). Once we swapped it out, no problems since and that was 5 years ago since to this last summer before picking up the jeep.
RevCo666 is offline   Quote Quick Reply
Old 01-21-2013, 09:38 PM   #8
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 32,401
Images: 2
Bad 02 sensors seldom trip the CEL light because it's hard for the ECM (engine computer) to know when it is providing bad data. 02 sensors eventually go bad and need to be replaced at certain intervals, just like spark plugs do. And when they go bad, it's common for them to cause the air/fuel mixture to go too rich.

And as said above, don't run 89, 91, or especially not 93 octane. Higher octanes don't burn any cleaner and they don't produce more power. In fact, the higher the octane, the harder it is for it to ignite and the slower it burns... just the opposite of what many people think.

Running too high of an octane can actually degrade engine performance and leave unburned deposits behind.
__________________
When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 01-21-2013, 09:49 PM   #9
Jeeper
 
jgorm's Avatar
 
Join Date: May 2010
Location: San Diego
Posts: 1,918
Quote:
Originally Posted by Jerry Bransford View Post
Bad 02 sensors seldom trip the CEL light because it's hard for the ECM (engine computer) to know when it is providing bad data.
Not totally true. The ECU knows exactly how much fuel it should add based on certain tables. The O2s give feedback to let the ecu know how close it really is. The fuel trims show EXACTLY how far off it is from stock. The one thing that is partly true is that it's difficult for O2s to throw codes because most ECUs (including wrangler's) throw the code when its past 25% off the normal.
__________________
my 06 LJ rubicon
2.5" SL, 1" BL, DIY highline, 35s with double beadlocks.
jgorm is offline   Quote Quick Reply
Old 01-21-2013, 09:51 PM   #10
Jeeper
 
jgorm's Avatar
 
Join Date: May 2010
Location: San Diego
Posts: 1,918
Quote:
Originally Posted by RevCo666 View Post
Would it be a waste of time to just change them anyways?
not at all. O2s are the most important sensor on any gas based vehicle. I replace them every 50K miles, or less if boosted or on juice.
__________________
my 06 LJ rubicon
2.5" SL, 1" BL, DIY highline, 35s with double beadlocks.
jgorm is offline   Quote Quick Reply
Old 01-21-2013, 11:06 PM   #11
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
Quote:
Originally Posted by jgorm View Post
not at all. O2s are the most important sensor on any gas based vehicle. I replace them every 50K miles, or less if boosted or on juice.
Ok, based on everyone opinion(which I appreciate big time!) I'll talk to my mechanic tomorrow as my jeep is already in the garage for a seperate issue(the passenger door wont open and I think its the pin/wire that connects to the cylinder lock is messed). I'de do the door myself but I cant even open it and working in -20c weather with no garage is not a fun thing hehe.

For a 2001 TJ 4.0 manual 5spd, there are 4 required O2 sensors? 2 in the front and 2 in the back? Searching the net and thats what I'm thinking based on this site mostly:

Experimental Insanity! - Jeep Oxygen Sensor FAQ

Sorry, but I'm a novice but trying to learn to do things for myself before running to my mechanic...
RevCo666 is offline   Quote Quick Reply
Old 01-21-2013, 11:40 PM   #12
Jeeper
 
Join Date: Jun 2012
Posts: 23
don't mess with the rear's they are just cat tattletales, fronts are always a good idea past 50-100k,
js35 is offline   Quote Quick Reply
Old 01-21-2013, 11:40 PM   #13
Jeeper
 
Join Date: Oct 2011
Posts: 1,606
Quote:
Originally Posted by jgorm View Post
Not totally true. The ECU knows exactly how much fuel it should add based on certain tables.
If that was totally true, there would be no need for upstream oxygen sensors.
tangofox007 is offline   Quote Quick Reply
Old 01-22-2013, 10:56 AM   #14
Jeeper
 
jgorm's Avatar
 
Join Date: May 2010
Location: San Diego
Posts: 1,918
Quote:
Originally Posted by tangofox007 View Post
If that was totally true, there would be no need for upstream oxygen sensors.
No, it is true. I've spend many hours going over how the ECU programming works on my 06 wrangler. I've tuned over 500 cars since I started tuning as a side job. The purpose of the O2s is to be able to adjust for other things as parts wear. The ECU does know exactly how much fuel to add based on the MAP, IAT, ECT, and TPS sensors. You can unplug your O2s and the ECU will run off these tables. If your jeep had all brand new parts you could run without O2 sensors. Once these sensors start to loose a bit of their calibration, the O2s become even more important. Remember that WOT open loop fuel is not based on the O2s at all, and that is where the fueling is even more important. (there is a max 2.15% correction that the O2s can save to the ECU that will adjust the WOT fuel) Wranglers wont go open loop until at least 14.4 seconds after WOT, and longer if the ECT is cool. (75 seconds at -20C)
__________________
my 06 LJ rubicon
2.5" SL, 1" BL, DIY highline, 35s with double beadlocks.
jgorm is offline   Quote Quick Reply
Old 01-22-2013, 10:59 AM   #15
Jeeper
 
Join Date: Oct 2011
Posts: 1,606
Quote:
Originally Posted by jgorm View Post
No, it is true.
Your own explanation contradicts that notion.

Your theory is comparable to claiming that a yardstick knows exactly how long an inch is, so there is never a need for a micrometer.
tangofox007 is offline   Quote Quick Reply
Old 01-22-2013, 11:05 AM   #16
Jeeper
 
jgorm's Avatar
 
Join Date: May 2010
Location: San Diego
Posts: 1,918
Quote:
Originally Posted by tangofox007 View Post
Your own explanation contradicts that notion.
No it doesn't. How so? Maybe re-read the post that you quoted me on. The ecu knows exactly how much fuel to add when all the sensors other than the O2s are in calibration.
__________________
my 06 LJ rubicon
2.5" SL, 1" BL, DIY highline, 35s with double beadlocks.
jgorm is offline   Quote Quick Reply
Old 01-22-2013, 07:26 PM   #17
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
Quote:
Originally Posted by js35 View Post
don't mess with the rear's they are just cat tattletales, fronts are always a good idea past 50-100k,
Well I talked to my mechanic he said I may be wasting my time/money because the "check engine" light hasnt engaged... But I did get some quotes but I'm at a loss a side from knowing NGK does OEM for the jeep. The other types are Denso and Ac Delco. I was told to avoid Bosch as they are garbage...??? Any impressions or recommendations? I'm only gonna change both fronts in early spring. (getting my todo list in order by then...)
RevCo666 is offline   Quote Quick Reply
Old 01-22-2013, 07:29 PM   #18
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 32,401
Images: 2
I've yet to have a bad 02 sensor trip the CEL light in any of my vehicles. Your comments regarding the various 02 sensor brands are what I'd go along with as well. Check them out at RockAuto Parts Catalog where you may find them cheaper as well as lots of information on each brand they carry.
__________________
When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 01-22-2013, 07:32 PM   #19
Knows a couple things...

WF Supporting Member
 
Jerry Bransford's Avatar
 
Join Date: Nov 2005
Location: Escondido, Calif.
Posts: 32,401
Images: 2
Quote:
Originally Posted by js35 View Post
don't mess with the rear's they are just cat tattletales...
While that was true on my '97 TJ, that isn't true for newer TJs where the 02 sensor on the cat has been given more of an active role in checking the air/fuel mixture. I think that started somewhere around 2002 or 2003.
__________________
When you have a choice, buy American.

Jerry Bransford is online now   Quote Quick Reply
Old 01-22-2013, 07:54 PM   #20
Jeeper
 
jgorm's Avatar
 
Join Date: May 2010
Location: San Diego
Posts: 1,918
Quote:
Originally Posted by RevCo666 View Post
Well I talked to my mechanic he said I may be wasting my time/money because the "check engine" light hasnt engaged... But I did get some quotes but I'm at a loss a side from knowing NGK does OEM for the jeep. The other types are Denso and Ac Delco. I was told to avoid Bosch as they are garbage...??? Any impressions or recommendations? I'm only gonna change both fronts in early spring. (getting my todo list in order by then...)
Get the mopar ones. I can't even count how many issues I've dealt with due to knock off cheap O2s. They don't cost that much more.
Quote:
Originally Posted by Jerry Bransford View Post
While that was true on my '97 TJ, that isn't true for newer TJs where the 02 sensor on the cat has been given more of an active role in checking the air/fuel mixture. I think that started somewhere around 2002 or 2003.
The more active roll, is in determining the catalytic efficiency for the emissions changes they made in 02 on all vehicles. The rear o2 sensor, on any vehicle, will never change the fueling my more that 2% in the most extreme cases. This is because the cat will start to be more inefficient over time and using AFR data, post cat, is never really useful (except at WOT on a dyno when it's not convenient to install a wideband precat and the exhaust flow is so fast the cat wont change it by more than about half a point). Why would any OEM choose to use data that can be confounded by cat performance when they have data that is not altered by the cat at all??
__________________
my 06 LJ rubicon
2.5" SL, 1" BL, DIY highline, 35s with double beadlocks.
jgorm is offline   Quote Quick Reply
Old 01-23-2013, 07:08 PM   #21
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
Well I bit the bullet, and decided to go with NGK/NTK as they are OE for my jeep. Only purchased both fronts O2 sensors. Today was the pinnacle of my decision as my odometer read 148km for almost 3/4 of a tank (70liters). I know its mostly in town driving, and yes I have been using my 4 Hi for atleast half the time but really, I should be getting atleast 300 on a tank for city driving. So once my order is in, and its not -30c without the windchill, I'll do the switch. Thanks everyone who offered up some info.
RevCo666 is offline   Quote Quick Reply
Old 01-23-2013, 10:21 PM   #22
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
Quote:
Originally Posted by RevCo666 View Post
Well I bit the bullet, and decided to go with NGK/NTK as they are OE for my jeep. Only purchased both fronts O2 sensors. Today was the pinnacle of my decision as my odometer read 148km for almost 3/4 of a tank (70liters). I know its mostly in town driving, and yes I have been using my 4 Hi for atleast half the time but really, I should be getting atleast 300 on a tank for city driving. So once my order is in, and its not -30c without the windchill, I'll do the switch. Thanks everyone who offered up some info.
I also pulled the trigger on the NTK sensor. Hope to install in the next couple days. I also appreciate everyone's input, and will post in the next couple weeks with (hopefully good) results!
__________________
ranger44 is offline   Quote Quick Reply
Old 01-24-2013, 11:22 AM   #23
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
Quote:
Originally Posted by ranger44 View Post
I also pulled the trigger on the NTK sensor. Hope to install in the next couple days. I also appreciate everyone's input, and will post in the next couple weeks with (hopefully good) results!
Are you just changing the front 2 sensors or all four? As per earlier posts, I'm only going with the front two. Including cost of shipping way up here in Northern Ontario, its running me about 79$CAN. Its funny I checked how much the same ones my garage would charge me and just for both I was looking at 180$CAN... Crazy man... If possible lets try to keep the info going that way we can compare results... Sounds good?
RevCo666 is offline   Quote Quick Reply
Old 01-24-2013, 11:49 AM   #24
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
Quote:
Originally Posted by RevCo666 View Post

Are you just changing the front 2 sensors or all four? As per earlier posts, I'm only going with the front two. Including cost of shipping way up here in Northern Ontario, its running me about 79$CAN. Its funny I checked how much the same ones my garage would charge me and just for both I was looking at 180$CAN... Crazy man... If possible lets try to keep the info going that way we can compare results... Sounds good?
I only have the 4-cyl, so there are only two sensors total. I am only changing the front one as well based on both what people have said here, and the fact that the PO changed them. He SAID he changed both, but the only one that looks "new" is the downstream. This also make sense since I am still getting the CE light and code.

Will definitely keep the thread going in the coming weeks to compare results. Good Luck!
__________________
ranger44 is offline   Quote Quick Reply
Old 01-28-2013, 05:55 PM   #25
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
This didn't help my situation.

Click image for larger version

Name:	ForumRunner_20130128_185415.jpg
Views:	128
Size:	98.2 KB
ID:	203018



Click image for larger version

Name:	ForumRunner_20130128_185415.jpg
Views:	128
Size:	98.2 KB
ID:	203018
__________________
ranger44 is offline   Quote Quick Reply
Old 01-29-2013, 12:15 PM   #26
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
Quote:
Originally Posted by ranger44 View Post
This didn't help my situation.

Attachment 203018



Attachment 203018
When i got my jeep last summer, that was the first thing i asked to change when i brought to my mechanic. At first he was hesitant but afterwards he told me that it was a good call. My plugs were maybe not as bad as yours but close. Got my o2 sensors this morn, went to see my mechanic to double check the one i got. He's got the right tools to install so next monday is hopefully a better mpg day from then on.
RevCo666 is offline   Quote Quick Reply
Old 02-04-2013, 06:10 PM   #27
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
Installed my new NTK upstream sensor today and ran it for a few miles around town running errands (in the snow). No more CEL!!! Hopefully it stays off, however I am still getting DTC code 42. Any suggestions on what may be causing that? Also much fewer exhaust fumes smelled during driving and after about 30 minutes of idle. Happy for that as well.

Will keep you posted on how this effects my fuel economy.
__________________
ranger44 is offline   Quote Quick Reply
Old 02-04-2013, 06:11 PM   #28
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
Old and new

Click image for larger version

Name:	ForumRunner_20130204_191112.jpg
Views:	78
Size:	177.9 KB
ID:	205760
__________________
ranger44 is offline   Quote Quick Reply
Old 02-04-2013, 07:05 PM   #29
Jeeper
 
Join Date: Dec 2012
Posts: 2,631
After double checking my ntk o2 sensors, got them installed today BUT it turns out i had one front and one back... So now i have to reorder both same parts and pay another 100$for the second set. Doesnt pay trust professionals sometimes. Oh well atleast next week it will be done and over with... And hopefully better mpg.
RevCo666 is offline   Quote Quick Reply
Old 02-04-2013, 07:44 PM   #30
Jeeper
 
ranger44's Avatar
 
Join Date: Oct 2012
Location: Coumbus, Ohio
Posts: 64
Quote:
Originally Posted by RevCo666 View Post
After double checking my ntk o2 sensors, got them installed today BUT it turns out i had one front and one back... So now i have to reorder both same parts and pay another 100$for the second set. Doesnt pay trust professionals sometimes. Oh well atleast next week it will be done and over with... And hopefully better mpg.
Before you order, be sure to check, I BELIEVE, the downstream sensor is a different number than upstream sensor. Hopefully it works out for ya. I just hope I can figure out this stinking 42 code and be done with emissions problems

__________________
ranger44 is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may 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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off




Download our Mobile App

» Featured Product

All times are GMT -5. The time now is 06:56 PM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC