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-   -   TJ running rich (http://www.wranglerforum.com/f282/tj-running-rich-213736.html)

ranger44 01-21-2013 08:03 AM

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!!

jgorm 01-21-2013 10:31 AM

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.

Dextreme 01-21-2013 10:48 AM

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. :thumb:

RevCo666 01-21-2013 04:47 PM

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.

ranger44 01-21-2013 06:22 PM

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.

tangofox007 01-21-2013 06:53 PM

Quote:

Originally Posted by RevCo666 (Post 3257507)
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."

RevCo666 01-21-2013 09:29 PM

Quote:

Originally Posted by tangofox007 (Post 3258105)
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.

Jerry Bransford 01-21-2013 09:38 PM

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.

jgorm 01-21-2013 09:49 PM

Quote:

Originally Posted by Jerry Bransford (Post 3259194)
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.

jgorm 01-21-2013 09:51 PM

Quote:

Originally Posted by RevCo666 (Post 3259113)
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.

RevCo666 01-21-2013 11:06 PM

Quote:

Originally Posted by jgorm (Post 3259291)
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...

js35 01-21-2013 11:40 PM

don't mess with the rear's they are just cat tattletales, fronts are always a good idea past 50-100k,

tangofox007 01-21-2013 11:40 PM

Quote:

Originally Posted by jgorm (Post 3259280)
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.

jgorm 01-22-2013 10:56 AM

Quote:

Originally Posted by tangofox007 (Post 3259739)
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)

tangofox007 01-22-2013 10:59 AM

Quote:

Originally Posted by jgorm (Post 3261082)
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.

jgorm 01-22-2013 11:05 AM

Quote:

Originally Posted by tangofox007 (Post 3261091)
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.

RevCo666 01-22-2013 07:26 PM

Quote:

Originally Posted by js35 (Post 3259737)
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...)

Jerry Bransford 01-22-2013 07:29 PM

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.

Jerry Bransford 01-22-2013 07:32 PM

Quote:

Originally Posted by js35 (Post 3259737)
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.

jgorm 01-22-2013 07:54 PM

Quote:

Originally Posted by RevCo666 (Post 3263325)
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 (Post 3263359)
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??:doh:

RevCo666 01-23-2013 07:08 PM

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.

ranger44 01-23-2013 10:21 PM

Quote:

Originally Posted by RevCo666 (Post 3268522)
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!

RevCo666 01-24-2013 11:22 AM

Quote:

Originally Posted by ranger44 (Post 3269771)
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? :thumb:

ranger44 01-24-2013 11:49 AM

Quote:

Originally Posted by RevCo666 (Post 3271621)

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? :thumb:

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 01-28-2013 05:55 PM

1 Attachment(s)
This didn't help my situation.

Attachment 203018



Attachment 203018

RevCo666 01-29-2013 12:15 PM

Quote:

Originally Posted by ranger44 (Post 3290597)
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. :dance:

ranger44 02-04-2013 06:10 PM

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 02-04-2013 06:11 PM

1 Attachment(s)
Old and new

Attachment 205760

RevCo666 02-04-2013 07:05 PM

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.

ranger44 02-04-2013 07:44 PM

Quote:

Originally Posted by RevCo666 (Post 3320968)
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


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