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Need some help with O2 Sensors.....

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  • Need some help with O2 Sensors.....

    Hey guys.....What is the trick in gettin the front two O2 sensors off the manifolds? Is there a special tool I'll need? I have a 97 T/A.........thanks for any replies....

  • #2
    This will be a little bit of a chore if your manifolds are still on the car.

    First heavily spray the base of the o2 sensors with One Lube or a similar penetrating lubricant and let sit for about 15-30 minutes, those suckers are on there! Then unplug from the wire harness and then loosen with a 22mm or 7/8 wrench. You will have to put a little elbow grease into these

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    • #3
      Depending on how you can get to them, you may need an O2 sensor socket. Available at any auto parts store.
      Rob B 95Z A4 Tech Page (Part numbers / locations, how to's, schematics, DTC's...) Home Page - shbox.com

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      • #4
        PBlaster is the penetrating oil to use.... however, anytime you use a penetrating oil, the sensor will be contaminated and cannot be re-used so prepare to replace the sensors.

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        • #5
          The "O2 sensor socket" will definitely produce the best results. It is a heavy wall, 6 point design of the correct size, that will maximize contact and minimize problems with rounding the corners off the hex on the sensor. Joe's point about contamination is well taken.

          As I recall, the driver's side is on the base of the manifold and the passenger side is on the Y-pipe (at least on single-cat LT1's.... not sure about your dual-cat). The problem with the O2 socket is its bulk and the limited space available to fit it in. One option might be to drop the Y-pipe, but now you have to worry about breaking off the studs in the manifolds that the Y-pipe bolts to.... another problem.
          Fred

          381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

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          • #6
            Originally posted by Joe 1320
            PBlaster is the penetrating oil to use.... however, anytime you use a penetrating oil, the sensor will be contaminated and cannot be re-used so prepare to replace the sensors.
            This is a good point and would seem to be a problem but it really isn't thankfully. The actual "sensor tip" will rarely get any lubricant on it. I have removed quite a few f-body o2 sensors and I think only one got a little lube on it but even it worked fine and reported accurate voltage after reinstallation into a header.

            A 22mm wrench is a tight fit and will not round corners but the o2 sensor socket works fairly well too, but as Fred mentioned they can be bulky.

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            • #7
              I am in the process of putting a different y-pipe on the car. My old one had straight pipes welded in for the cats. I decided to purchase a used y-pipe and put it on. So the old one is off right now. I tried to get a wrench on the O2 sensors but there wasnt really any room to work. It looks like a pain. Im also going to change out those last couple plugs and wires i didnt get to last time.......I have already soaked them with PBlaster a couple days ago. And i already have new ones I am going to install.....so contamination wont matter. I think I will go purchase an O2 sensor socket later on today.....Any other suggestions? Thanks!

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              • #8
                There's a special antisieze that has crushed glass beads in it that is supposed to be used on the threads. And sometimes if it won't come out cold, it will come out better with the exhaust warmed up from running the car. As for plugs, get one of the short sockets sold on ebay for $7. You can put a wrench on it and get at plugs where's there no clearance.

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                • #9
                  The "contamination" problem is not related to the tip of the sensor.... its a problem with getting the penetrating oil in the passage that allows the outside air to reach the inside of the sensor membrane.
                  Fred

                  381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

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                  • #10
                    That is a good point. Maybe using a petroleum based lubricant isn't such a good idea altogether. I wonder if an alcohol/graphite mixture would contaminate the inner surface if it were applied to help loosen the sensor?

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                    • #11
                      Someday, I'm going to cut a sensor open and investigate just exactly how the sensor gets reference air. The book says thru the wire jacket, but I find that hard to believe - yet it might be true since any other opening might lend itself to contamination on a daiy basis such as rain water, car wash underbody flush, engine cleaning, etc. The other thing i'm curious about is that the amount of reference air must be very tiny, and it seems almost impossible that it is allowed to circulate in any appreciable manner, given the descriptions of how it is sampled. Maybe the answer is on the internet somewhere - also I'll check with the emissions guys at work to see what they say. This is important cause some guys have had problems with split BLMs after lengthening the wires to work with headers. I did it without probs, but would surely have bought the extenders instead if I had known about them.

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                      • #12
                        Its a mystery how the "vent" actually is set up. Every diagram I have seen is different, except for the fact that the membrane needs "air" on one side and exhaust on the other, to develop the voltage. I would think that water based contamination shouldn't be a problem, since they are hot enough to boil off any water, but it would cetainly leave a residue if there were any dissolved solids - e.g. road salt.

                        I've played around with an old sensor and a propane torch.... (it was a really "slow" day)...... Might be interesting to get it stable, record the voltage, then intentionally contaminate the area where the wires enter to see what happens.

                        The Bosch description says the "Reference outside air for the interior of the thimble comes from a hole in the sensor shell, or through the wiring connector." But they don't show it on their diagram.....

                        Fred

                        381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

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                        • #13
                          My best guess would be that the air being referanced might not be literally vented to amosphere. There appears to be air "pockets" within the sensor body itself with seals from the "hot" end and the opposite end with the protruding wires. Since these are not assembled within a vacuum it would make sense that the sample would be protected from usual road debris and moisture, but a penetrating oil can breach the seals around the wiring and contaminate the interior of the body.

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                          • #14
                            I know one of the R&D guys at NGK - I'll ask him and post if he gives me a meaningful answer.
                            -----------
                            OK - I got answers. My contact says there are several types:

                            1. Sensor gets air through a filter located near where the wires come out.

                            2. Sensor gets air which is wicked through the wire and is introduced to the wire at the connector end.

                            3. The UEGO type sensors manufacture air for it's O2 reference through a chemical change inside the sensor using the electricity and heat to produce ions. WHEW!

                            Anyway, in case you ever wondered, there you have it.

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                            • #15
                              Originally posted by Kevin - Blown 95 TA
                              I know one of the R&D guys at NGK - I'll ask him and post if he gives me a meaningful answer.
                              -----------
                              OK - I got answers. My contact says there are several types:

                              1. Sensor gets air through a filter located near where the wires come out.

                              2. Sensor gets air which is wicked through the wire and is introduced to the wire at the connector end.

                              3. The UEGO type sensors manufacture air for it's O2 reference through a chemical change inside the sensor using the electricity and heat to produce ions. WHEW!

                              Anyway, in case you ever wondered, there you have it.
                              Yes I also talked to Fuel Injection Specialties here in San Antonio and they basically said the same thing that you said Kevin - Blown 95 TA. So it is OK afterall to use a lubricant to break em loose but you just have to be careful and only spray the base.

                              Here is one of my old manifolds with the O2 sensor still there, sorry about the focus:

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