TJ sputters while accelerating


MOTOcity

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Dec 19, 2018
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Salt Lake City
my 97 started sputtering on acceleration a few days ago. my initial assumption was either fuel pump or fuel injectors. a day before the sputtering a smelled a ton of gas in cab. The check engine light comes on and threw code for fuel injectos. I had a shop test injectors and they were firing fine. i read on another forum that it could be a bad computer? suggestions before i cough up 250 for a new computer?
 

Jerry Bransford

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dont remember the exact code. guy at autozone just said fuel injectors
Pay NO attention to what any counter salesperson says at Autozone, they're not mechanics and few know what they're talking about.

What is most likely bad is the upstream O2 sensor. That's what sets the air-fuel mixture ratio and when they go bad, they cause bad performance, sputtering, and a strong gas smell. And they do go bad, they're kind of like a spark plug in that they need to be replaced at appropriate intervals.

If you replace your upstream O2 sensor, make sure to ONLY go with an NTK O2 sensor... avoid Bosch O2 sensors which don't work well in our Jeeps.

If your Jeep seems to run better when it's cold and it starts running badly once it starts warming up that's about a 99.9999% assurance the problem is caused by that bad upstream O2 sensor. The downstream O2 sensor on the catalytic converter does not need to be replaced, it has nothing to do with this problem.

Do you have the 2.5L or 4.0L engine?
 
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Jerry Bransford

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2.5.

This will be the first time I replace this sensor on this jeep. Easy swap right?
You want the NTK 23506 sensor like at https://www.amazon.com/dp/B000C5O02M/?tag=wranglerorg-20 Better auto parts stores carry it, make sure NOT to buy a Bosch.

It may be an easy swap, you just need a 7/8" combination box-end/open-end wrench. Start the engine, get the exhaust system hot. O2 sensors are sometimes hard to get out when they're cold as they have often seized in place. Stop the engine, cut the wire coming out of the top of the old upstream O2 sensor. Slip the box-end of the wrench over it and unscrew it. For installing the new sensor I'd buy a slotted O2 sensor socket which fits on a ratchet wrench. The slot is for the new O2 sensor's wiring to fit into. That slotted O2 sensor socket is normally not strong enough to remove a seized O2 sensor which is why I suggested a 7/8 combination wrench, its box-end is strong strong enough no matter what.
 
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MOTOcity

MOTOcity

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Salt Lake City
You want the NTK 23506 sensor like at https://www.amazon.com/dp/B000C5O02M/?tag=wranglerorg-20 Better auto parts stores carry it, make sure NOT to buy a Bosch.

It may be an easy swap, you just need a 7/8" combination box-end/open-end wrench. Start the engine, get the exhaust system hot. O2 sensors are sometimes hard to get out when they're cold as they have often seized in place. Stop the engine, cut the wire coming out of the top of the old upstream O2 sensor. Slip the box-end of the wrench over it and unscrew it. For installing the new sensor I'd buy a slotted O2 sensor socket which fits on a ratchet wrench. The slot is for the new O2 sensor's wiring to fit into. That slotted O2 sensor socket is normally not strong enough to remove a seized O2 sensor which is why I suggested a 7/8 combination wrench, its box-end is strong strong enough no matter what.

isnt there supposed to be some sort of wire attached to that sensor in your link?
 
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MOTOcity

MOTOcity

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You want the NTK 23506 sensor like at https://www.amazon.com/dp/B000C5O02M/?tag=wranglerorg-20 Better auto parts stores carry it, make sure NOT to buy a Bosch.

It may be an easy swap, you just need a 7/8" combination box-end/open-end wrench. Start the engine, get the exhaust system hot. O2 sensors are sometimes hard to get out when they're cold as they have often seized in place. Stop the engine, cut the wire coming out of the top of the old upstream O2 sensor. Slip the box-end of the wrench over it and unscrew it. For installing the new sensor I'd buy a slotted O2 sensor socket which fits on a ratchet wrench. The slot is for the new O2 sensor's wiring to fit into. That slotted O2 sensor socket is normally not strong enough to remove a seized O2 sensor which is why I suggested a 7/8 combination wrench, its box-end is strong strong enough no matter what.
You are a true guru. I disconnected battery to reset engine light then drove it around to set it off again. Code is p0171 bank 1 too lean. This calls for replacement of down stream 02 SENSOR right? Jeep runs fine on a cold start but after engine warms up it starts to sputter and idle poorly. Scent of gas also fills the cab
 
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MOTOcity

MOTOcity

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You are a true guru. I disconnected battery to reset engine light then drove it around to set it off again. Code is p0171 bank 1 too lean. This calls for replacement of down stream 02 SENSOR right? Jeep runs fine on a cold start but after engine warms up it starts to sputter and idle poorly. Scent of gas also fills the cab
You are a true guru. I disconnected battery to reset engine light then drove it around to set it off again. Code is p0171 bank 1 too lean. This calls for replacement of down stream 02 SENSOR right? Jeep runs fine on a cold start but after engine warms up it starts to sputter and idle poorly. Scent of gas also fills the cab
nevermind. I just read upstream. Now does anyone have a photo that can show me location? I kmow its on the right side somewhere but i can't tell for sure from the stuff I see on the interwebs
 

Wes5395

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Florida
nevermind. I just read upstream. Now does anyone have a photo that can show me location? I kmow its on the right side somewhere but i can't tell for sure from the stuff I see on the interwebs

DC46FC05-B0A1-4817-960D-CBE78A1C46A7.png
 

Bennyggg

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Nov 8, 2019
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Location
Vista CA
Similar problem happened to me the other day. Driving home form work in a bit of a traffic jam noticed sputtering at low RPM and much reduced power. Also had a rich exhaust smell. Changed out the upstream O2 with an NTK 23151. Drove around today and the problem still exists. Decided to unplug the O2 sensors to make the computer move to default settings. Drove a bit and problem still exists.
Details:
99 4.0 175000 miles manual 32s stock gears
Owned for 5 years
The only recent engine work was coolant flush, new water pump, new thermostat/housing, fan clutch and hoses
Sputters at low RPM acceleration
Felt lack of power
Rich smell
No codes

looking for common causes for this issue to hammer out a plan to solve the problem. Any help would be great.

Ben
 

Karlson Drendel

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Joined
Oct 15, 2018
Messages
1
Location
Washington
@Jerry Bransford
Jerry, you're a wizard.
Just wanted to give this a bump here, my 97 2.5 TJ is losing power, bucking, and sputtering on the freeway. It still happens at low speeds, but driving to work on the 50 MPH freeway with my jeep is about killing me. No codes. I replaced the IAC, TPS, and have had a consistent issue with misfires and sputtering. In the diagram posted it looks like there's 4 O2 Sensors. Is that correct? If so, is it recommended to replace all of them to solve this problem? If not which ones should be replaced first?
Thanks,
-Karl
 

justfixedthat...

TJ Enthusiast
Joined
Jan 20, 2020
Messages
122
Location
Texas
Pay NO attention to what any counter salesperson says at Autozone, they're not mechanics and few know what they're talking about.

What is most likely bad is the upstream O2 sensor. That's what sets the air-fuel mixture ratio and when they go bad, they cause bad performance, sputtering, and a strong gas smell. And they do go bad, they're kind of like a spark plug in that they need to be replaced at appropriate intervals.

If you replace your upstream O2 sensor, make sure to ONLY go with an NTK O2 sensor... avoid Bosch O2 sensors which don't work well in our Jeeps.

If your Jeep seems to run better when it's cold and it starts running badly once it starts warming up that's about a 99.9999% assurance the problem is caused by that bad upstream O2 sensor. The downstream O2 sensor on the catalytic converter does not need to be replaced, it has nothing to do with this problem.

Do you have the 2.5L or 4.0L engine?
What if it runs that way cold too? Amid other symptoms (bucking and stalling), today I noticed sputtering, gas smell form the exhaust, and lack of power (sitting in Park I have to go pretty close to the floor to get the RPMs past 2000).
 

justfixedthat...

TJ Enthusiast
Joined
Jan 20, 2020
Messages
122
Location
Texas
Similar problem happened to me the other day. Driving home form work in a bit of a traffic jam noticed sputtering at low RPM and much reduced power. Also had a rich exhaust smell. Changed out the upstream O2 with an NTK 23151. Drove around today and the problem still exists. Decided to unplug the O2 sensors to make the computer move to default settings. Drove a bit and problem still exists.
Details:
99 4.0 175000 miles manual 32s stock gears
Owned for 5 years
The only recent engine work was coolant flush, new water pump, new thermostat/housing, fan clutch and hoses
Sputters at low RPM acceleration
Felt lack of power
Rich smell
No codes

looking for common causes for this issue to hammer out a plan to solve the problem. Any help would be great.

Ben
Same symptoms here. What was your solution?

Did yours buck and stall (separately)?
 

justfixedthat...

TJ Enthusiast
Joined
Jan 20, 2020
Messages
122
Location
Texas
@Jerry Bransford
Jerry, you're a wizard.
Just wanted to give this a bump here, my 97 2.5 TJ is losing power, bucking, and sputtering on the freeway. It still happens at low speeds, but driving to work on the 50 MPH freeway with my jeep is about killing me. No codes. I replaced the IAC, TPS, and have had a consistent issue with misfires and sputtering. In the diagram posted it looks like there's 4 O2 Sensors. Is that correct? If so, is it recommended to replace all of them to solve this problem? If not which ones should be replaced first?
Thanks,
-Karl
Same symptoms here, but also stalling. I haven't gone over 55 one the freeway in years because it misfires over that. But recently its been bucking, stalling, and now has low power and gas smell. How'd you fix it? Thanks
 

COYOTE83

Member
Joined
May 23, 2021
Messages
72
Location
Georgia
So I just saw this older thread that was bumped, I’m not having these issues myself but I read the thread just to gain a little knowledge, and I had an idea:
Do ythink it’s a good idea if someone makes a thread listing out some particulars with our TJs like @Jerry Bransford pointed out with using the NTK O2 sensor instead of the Bosch sensor and similar tips like that? It could save some people money and a potential headache from having to replace the parts again down the road due to installing a part like the Bosch O2 sensor that “doesn’t do good in our Jeeps”

there may already be a thread like that, I just haven’t found it.

I know a lot of the information and tips are subjective and preference and brand loyalty etc etc but I think it would be beneficial to have some of the more experienced members just list out some suggestions and specific parts, sensors, and things like that, that THEY use and maybe a quick reason why they use that particular sensor or whatever, to help guide some folks in the right direction.

maybe it would turn into another oil debate thread, but
it could possibly be a good “quick reference” resource some of the newer members and people new to jeeping in general could look at and think
“Well this member has been around a while and has some credibility and suggests to use “brand x” O2 sensors instead of “brand y” because of this reason” and it could help the people with less experience make more informed decisions. Maybe. Lol.

if anyone thinks it’s a good idea, feel free to start the thread with parameters you choose. If not, oh well it was just an idea. (Upped my post count tho! Lol)
and if there is already a thread like that please link it for me.

sorry for the thread hijack. Carry on.
 
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