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TJ sputters while accelerating

MOTOcity

Member
Joined
Dec 19, 2018
Messages
36
Location
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

TJ Guru
Supporting Member
Joined
Nov 9, 2015
Messages
12,288
Location
Escondido California
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

TJ Guru
Supporting Member
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Nov 9, 2015
Messages
12,288
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Escondido California
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

Member
Joined
Dec 19, 2018
Messages
36
Location
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?
 

tquig01

TJ Enthusiast
Joined
Mar 12, 2018
Messages
359
Location
Brewerton, NY, USA
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.
I had unfortunately changed mine and used Bosch before I found this forum. Guess who was replacing the O2 sensors again 3 months later...
 
OP
MOTOcity

MOTOcity

Member
Joined
Dec 19, 2018
Messages
36
Location
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.
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

Member
Joined
Dec 19, 2018
Messages
36
Location
Salt Lake City
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
 

Bennyggg

New Member
Joined
Nov 8, 2019
Messages
1
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