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Old 05-28-2012, 09:47 PM
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OxySensor Fiasco

Hi Everybody, I've never needed to replace an O2 sensor till now. It ain't coming out. Spent nearly a couple days and the only progress I've made is discovering what I would have done to engineer a better system.

The car wouldn't idle in gear without a slight power brake manipulation.
Unhooked O2 sensor and now I don't need to keep one foot on brake & one on gas to idle in gear. I've used a torch and a wide assortment of tool combinations to get the sensor to brake free. Now the hex on the sensor won't hold a socket without slipping.

At this point I'm down to figuring I'll leave it in for now, braze up the top to stop an exhaust leak where the guts/wire of the sensor broke out and fool the ECM into thinking the sensor is working (see below).

Surely someone has done this too. I was hoping for advice on the best way to rig a variable resistor up to the single wire going to the ECM. That way I could fine tune the fuel to rich or lean according to what I want for any senario; and I was thinking this would be beneficial to maybe injecting hydrogen and I could adjust the voltage for a leaner gas mixture for that purpose without a MAP enhancer???

It's on an '88 Regal -4 speed auto - 2.8 liters - no room to get a straight shot at the sensor or turn a tool against the firewall for a solid bite.

Any advice welcomed to steer me into a better direction. If I pull the engine or slightly hoist it at some future point, I'll replace the sensor unless what I'm thinking works better for my purposes.
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Old 05-29-2012, 01:06 AM
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Personally, Id focus on getting the sensor out. Depending on accessibility, you might try tack welding a "disposable" open-end wrench onto it to break it loose. Just keep in mind that youre gonna have to break the wrench free afterwards.
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Old 05-29-2012, 05:25 AM
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A pipe wrench will grip it if it's rounded off. Whether there's room to swing it under the vehicle, I cannot say- but if it was up on a rack or safely jacked up and supported w/jackstands, you will likely have enough room.

A page that may help is here.

Good luck.
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Old 05-29-2012, 08:04 AM
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OxySensor Fiasco

Hi CDJr. I don't have an electric welder, only an oxy/acet torch. Using a size "0" welding tip is taking too long to heat, so I'm going to get a #4 at Harbor Freight today or tomorrow. Since a #4 is rated for welding 1/4" material, I may give that a try. I am
hesitant though, 'cause I don't want to do any damage that would require repairing the exhaust manifold. Better to leave as is and do the mod I mentioned in the beginning. That way I can still use the vehicle and get it inspected here in WV. Repairing the manifold is going to require removing the head for sure. I can't sacrifice that much time and pain. Don't care about sacrificing a tool to get a job done though. Thanks for the idea. I haven't got that far in thinking of alternatives yet.
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Old 05-29-2012, 08:31 AM
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Make or buy an o2 wiring extension and weld in a bung just past the manifold. Use that exhaust sealant paste to plug the old o2 sensor if it leaks.

It's not ideal but it'll work just fine and much better than a resistor giving a false reading.
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Old 05-29-2012, 08:33 AM
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OxySensor Fiasco

Hi cobalt327. Thanks for the link. I'll spend more time on that later. Good stuff! I started by renting an O2 sensor tool kit from AutoZone and following the Service Manual instructions by getting the engine hot. That didn't work. I shoulda known that 99% of the time a 24 year old 02 sensor is not going to come out that way. By this time the ceramic broke out of the sensor so I jerked the wire out and went for a 7/8" 6 pt. impact socket and a 3/4" drive breaker bar with a 3 ft. cheater pipe. If I had a torch at the time, that would've probably worked, but instead started slipping because I needed a MAC universal inpact swivel. The angle was too great to get a solid turn on the bar. Then I went to a 22mm 6 pt. impact socket. I could keep that socket on a while before it started slipping. Then got the torch & tried heating the sensor and hammering a 21mm socket on. Couldn't get a solid blow. Yesterday was pipe wrench day! I've got a dozen pipe wrenches ranging from the 1940's era to modern design. Not enough room. Tried removing a heat shield from the firewall to gain some clearance, but the nut who designed that had steel hydraulic line routed through a channel in it. Only way that is coming out is bend and disconnect lines and looked like I would still have to cut it in half to get it out. Nothing is going to happen from underneath the car. this is purely a top-side job!

Gotta tend to some business today, before trying again. Still would like to hear of a way to bypass the need for an 02 sensor though. I have a rheostat, just need to envision this idea better. Definitely don't want to damage the manifold. That looks like the way it's headed in the process. Any 02 sensor bypass ideas?
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Old 05-29-2012, 08:51 AM
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OxySensor Fiasco

Hi ap72. There's barely enough room to get a torch or tool in the area of the existing sensor, let alone look for another bung location. I don't care about a false reading occasionally. I'm immune to seeing the engine light on this car and it runs better without the sensor than it did with the defective sensor hooked up. My main concern in the last couple of days was to stop the exhaust leak so I could get it inspected. Anything more in the direction of a "Normal" repair is icing on the cake!, but I would still like "electrical mod" ideas for now to save time & sweat.
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Old 05-29-2012, 09:57 AM
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If this is a 1 wire sensor:
You can mount a new sensor bung, further down the exhaust pipe where install is easier
by converting to a 3 wire or 4 wire heated type sensor.

The heater circuit just needs a simple 12v+ fused circuit switched by the ignition key.
You jerry rig plan to control the ECM will not work.
The O2 sensor and ECM do not interact like that.

When in "closed loop" the ECM is constantly shifting the AFR rich /then lean

the O2 sensor voltage output rapidly outputs a voltage +/- .450 V accordingly.

The The ecm only reads wether the sensor output voltage is above or below

the .450 MV cross over point. It will not react to a steady voltage.

it only reacts to the hi low switch in O2 voltage not the actual voltage. Or a steady voltage.

If you were to read the O2 voltage out put with a AFR gauge while the ECM is working and using the O2 sensor output o the trim the AFR (closed loop mode)
you would see the AFR gauge display rapidly switch back and forth rich lean rich lean.
When you rug the throttle it will go rich.

Last edited by F-BIRD'88; 05-29-2012 at 10:07 AM.
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Old 05-29-2012, 10:04 AM
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OxySensor Fiasco

Well, I know it wouldn't be a good idea to take voltage from any other sensor or ECM wiring for a mod. That means running a wire from higher voltage and stepping it down from 12v to 1 volt and then having a rheostat to adjust from 1 volt to .4 or so?
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Old 05-29-2012, 10:08 AM
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Quote:
Originally Posted by F-BIRD'88
If this is a 1 wire sensor:
You can mount a new sensor bung, further down the exhaust pipe where install is easier
by converting to a 3 wire or 4 wire heated type sensor.

The heater circuit just needs a simple 12v+ fused circuit switched by the ignition key.

Yes F-BIRD'88, it's a single wire sensor. Thanks for that idea, but wouldn't it be more apt to give false readings further away from the cyl. head? And where would one hook the other two wires on such a wide band sensor in an OBD1 setup?
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Old 05-29-2012, 10:08 AM
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Quote:
Originally Posted by B-1
Well, I know it wouldn't be a good idea to take voltage from any other sensor or ECM wiring for a mod. That means running a wire from higher voltage and stepping it down from 12v to 1 volt and then having a rheostat to adjust from 1 volt to .4 or so?
it don;t work like that. Some people should just stay away from cars.
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Old 05-29-2012, 10:15 AM
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Quote:
Originally Posted by B-1
Yes F-BIRD'88, it's a single wire sensor. Thanks for that idea, but wouldn't it be more apt to give false readings further away from the cyl. head? And where would one hook the other two wires on such a wide band sensor in an OBD1 setup?
This is not WIDE BAND it is narrow band. The only difference is the heater circuit.

it is the same narrow band sensor with a heater circuit added.

1 wire is the sensor output, the other two wires are for the heater.

The heater maintains the required minimum sensor temp so it can function without being on the ex manifold

any fused 12V circuit that is switched by the key will run the heater circuit.

You are lost on all this stuff. If you had just used a proper O2 sensor socket tool in the first place and done it on a dead cold engine, the thing would have come right out.

if the exhaust system or ex manifold has leaks the sensor will not function.

Once you get the o2 sensor fixed you will probabily need to clear any hard codes stored on the ECM or it will continue to run on open loop "limp home" mode.

put some thread anti-sieze compound on the new sensor.
Don't get it all over the sensor. a little bit on the threads goes a long way.

Last edited by F-BIRD'88; 05-29-2012 at 10:23 AM.
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Old 05-29-2012, 10:21 AM
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Quote:
Originally Posted by F-BIRD'88
it don;t work like that. Some people should just stay away from cars.

The ECM is getting no feedback from an 02 sensor as it now stands and for the most part it runs just fine on the preprogrammed tables on the chip. Sometimes the engine light doesn't come on, but the fuel is rich.

What about a PWM to vary the voltage in the appropriate range? I think what you are talking about would be more critical on a wide band OBD2 system. As I said, I haven't had much reason to consider the workings of an 02 sensor in the scheme of things until now; weighing my options as it were - slanting towards something less "cheater bar" fashioned.
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Old 05-29-2012, 10:26 AM
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Quote:
Originally Posted by F-BIRD'88
This is not WIDE BAND it is narrow band. The only difference is the heater circuit.

it is the same narrow band sensor with a heater circuit added.

1 wire is the sensor output, the other two wires are for the heater.

The heater maintains the required minimum sensor temp so it can function without being on the ex manifold

any fused 12V circuit that is switched by the key will run the heater circuit.

You are lost on all this stuff. If you had just used a proper O2 sensor socket tool in the first place and don it on a dead cold engine, the thing would have come right out.

if the exhaust system has leaks the sensor will not function.
Read my other posts about tools and techniques used so far!
Of course you wouldn't remove a cold rusty 22 year old sensor
without some kind of tactic!
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Old 05-29-2012, 10:31 AM
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You are being an idiot. (And it won;t work) Just take the car to an exhaust shop and they will get the old sensor out for you.
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