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Finally replaced the 33 year old 02 sensor.


Broncotim

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Boy what a challenge and to change.1st the location of the sensor on my 1988 was in a awkward location. Located on angle pointing up just before the converter. Can not get a impact wrench in there. Finally after soaking with Kroil for two weeks. The use of a angled breaker bar and a 5 point socket and a lot of strength it finally moved. It was tuff every crank. Good news after the install of the new o2 sensor it seems to run smoother with more pep. Good luck changing yours.
 


Uncle Gump

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Yeah they can be pretty stubborn. Glad you got it out and is running better.
 

tw205

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Just change the same one in my 89. Mine was snapped off as well. I gave up trying to change it prior because like you said it a bear to get to. Fortunately or unfortunately my muffler rusted out so I took the opportunity to take it all off. Y pipe to tail pipe. Heated up the bung hole and took an impact to it. Came right out. Cats looked good , clean screens. Fit a new muffler, it’s a turbo flow, a few repairs the the tail pipe. Welded her all up. A couple new hangers and blamo!! I’m good to go. No more CEL. Bonus. 😎
 

LeBronCo

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Boy what a challenge and to change.1st the location of the sensor on my 1988 was in a awkward location. Located on angle pointing up just before the converter. Can not get a impact wrench in there. Finally after soaking with Kroil for two weeks. The use of a angled breaker bar and a 5 point socket and a lot of strength it finally moved. It was tuff every crank. Good news after the install of the new o2 sensor it seems to run smoother with more pep. Good luck changing yours.
Boy what a challenge and to change.1st the location of the sensor on my 1988 was in a awkward location. Located on angle pointing up just before the converter. Can not get a impact wrench in there. Finally after soaking with Kroil for two weeks. The use of a angled breaker bar and a 5 point socket and a lot of strength it finally moved. It was tuff every crank. Good news after the install of the new o2 sensor it seems to run smoother with more pep. Good luck changing yours.
What symptoms were you experiencing before you changed it?
 

Broncotim

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The bronco II would not idle correctly and was getting awful fuel mileage.
 

LeBronCo

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The bronco II would not idle correctly and was getting awful fuel mileage.
My 87 is getting poor mileage also. Most noteworthy is how it behaves on a hill. I cannot get past 1800 rpms in third gear. It just won't power up. Does a backpressure test include the O2 sensor?
 

Uncle Gump

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Typically they remove an O2 sensor to connect a pressure gauge into the O2 sensor exhaust bung. The old sensor threads would be recoated with special anti seize and re-installed.

An O2 sensor would have zero to do with exhaust back pressure.
 

LeBronCo

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Typically they remove an O2 sensor to connect a pressure gauge into the O2 sensor exhaust bung. The old sensor threads would be recoated with special anti seize and re-installed.

An O2 sensor would have zero to do with exhaust back pressure.
OK so how do I know if I have a bad O2 sensor? What are the symptoms?
 

Uncle Gump

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Typically it would be noted as a drop in fuel economy without any other noticeable drivability symptoms. They are essentially a battery that is capable of generating 1 volt. A chemical reaction happens when the inside of the sensor is vented to the atmosphere and the outside of the sensor is exposed to the exhaust stream. The higher the oxygen content in the exhaust... the more voltage it will produce. But being a battery they wear out. Typically north of 100K on an O2 sensor it will start to lose it generating potential. This issue is much easier to see on vehicles with OBDII. You can actually monitor O2 voltage. OBDI system can't do this. They're also prone to failing with the use of some of the older silicone sealants. Most of them these days are O2 sensor safe. But if the wrong type was used... it coats the outer layer of the O2 sensor thimble and renders them inoperative. Most time they will set codes to when failing but not always.

If this is the same symptom you've been dealing with for months... I kinda doubt it's an O2 issue. But... if it's the original it certainly can't hurt to install a new one.
 

LeBronCo

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Typically it would be noted as a drop in fuel economy without any other noticeable drivability symptoms. They are essentially a battery that is capable of generating 1 volt. A chemical reaction happens when the inside of the sensor is vented to the atmosphere and the outside of the sensor is exposed to the exhaust stream. The higher the oxygen content in the exhaust... the more voltage it will produce. But being a battery they wear out. Typically north of 100K on an O2 sensor it will start to lose it generating potential. This issue is much easier to see on vehicles with OBDII. You can actually monitor O2 voltage. OBDI system can't do this. They're also prone to failing with the use of some of the older silicone sealants. Most of them these days are O2 sensor safe. But if the wrong type was used... it coats the outer layer of the O2 sensor thimble and renders them inoperative. Most time they will set codes to when failing but not always.

If this is the same symptom you've been dealing with for months... I kinda doubt it's an O2 issue. But... if it's the original it certainly can't hurt to install a new one.
Unc, this is the weirdest 2.9 ever in my 87. After replacing the tank, both pumps/filters, new dist. w/TPS, MAP sensor, wires, plugs, timing, it was noticeably better. After running a couple cans of Seafoam through a few tanks of gas it seemed to be getting even better. Checked a fuel injector and the mechanic said it looked fine. However I am only getting around 7-8mpg. ????? It idles and revs nicely. Under load it struggles and on a hill I can't get past 1800 rpm in 3rd gear. So, I'm thinking 02 sensor and injectors. Can't hurt right? only the pocketbook.
 

Uncle Gump

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I know you said you had it checked for a restricted exhaust... but I would be really tempted to disconnect the exhaust in front of the cat and go give it a serious rip.
 

LeBronCo

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I know you said you had it checked for a restricted exhaust... but I would be really tempted to disconnect the exhaust in front of the cat and go give it a serious rip.
Gonna be loud as hell! If it's a simple (haha) unbolt, I'll give it a try.
 

Groovtubin

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Boy what a challenge and to change.1st the location of the sensor on my 1988 was in a awkward location. Located on angle pointing up just before the converter. Can not get a impact wrench in there. Finally after soaking with Kroil for two weeks. The use of a angled breaker bar and a 5 point socket and a lot of strength it finally moved. It was tuff every crank. Good news after the install of the new o2 sensor it seems to run smoother with more pep. Good luck changing yours.
AWSM! FWIW, my Bronco II has same paint scheme as yours! Just went thru the ignition top to bottom, still has a SLIGHT miss, im thinkin ta change the O2 as well, is it a 3 pin connector? Thanks, n thx for the data!
 

custombolt

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Just to start at step one - Did you all disconnect the spout before you set the timing?
Next is spark plug wires. Weak ones can be finicky. Wear rubber gloves and pull one plug wire at a time. All wires should have the same effect on the sound of the engine at idle.
 

adrian p

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i am wondering if i have an o2 sensor or map sensor going bad. My daughters new 1986 b2 just started having a flashing emiss light but she stated it runs and sounds fine. Any help would be aprreciated. It has the 4.0 and a magnaflow exhaust.
 

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