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  1. #1
    la vache fantôme phantomcow2's Avatar
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    Can I run without an O2 sensor for a day?

    I just installed headers on my car. That whole pipe was damn near falling apart, and a mechanic confirmed that I have an exhaust leak. So, I fixed that problem. I installed it and took it for a 2 mile test run. First impressions; I definitely did not lose any low end torque. The car doesn't sound much different, which is fine. I am definitely feeling a slight increase of power, particularly above 2500rpm.

    My concern:
    The header relocated the oxygen sensor to be more underneath the car, so I had to remove the O2 sensor to get it all to fit, since the original sensor wire was probably 16" too short. I plan to cut and lengthen the wire and re install it tomorrow.
    Am I doing any damage to any components by not having the oxygen sensor up and running for a day? I'll drive 21 miles tomorrow without it. If it's serious and critical that I have it running, I can get up early and install it before work. But if it's not going to cause any issues for such a short trip, I'd rather just do it after work.
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  2. #2
    la vache fantôme phantomcow2's Avatar
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    By the way, these headers get really hot. Maybe it's just because I opened the hood right after I ran it, but it was radiating with heat and looked like it turned yellow very slightly. Is this alright?
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  3. #3
    Air
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    Destroyer of Wheels Air's Avatar
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    When the O2 sensor went on my truck it ate through gas - like down to about 5 mpg. Also when it got to temperature it ran like crap. No damage though.

    The headers may have come with a coating that will smoke and burn off.

  4. #4
    Non Tribuo Anus Rodentum and off to the next adventure (RIP) Stacey's Avatar
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    Use header wrap to insulate them.

  5. #5
    Senior Member Michigander's Avatar
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    Order some O2 simulators and be done with it.
    Bring back the Sig Test!


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  6. #6
    The Site Administrator: Currently at home recovering from a couple of strokes,please contact my assistnt admins for forum issues Tom Stormcrowe's Avatar
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    Your headers will get HOT! That's for sure.
    on light duty due to illness; please contact my assistants for forum issues. They are Siu Blue Wind, or CbadRider or the other 3 star folk. I am currently at home recovering from a couple of strokes. I am making good progress, happily.


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  7. #7
    Footballus vita est iamlucky13's Avatar
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    Quote Originally Posted by Air View Post
    When the O2 sensor went on my truck it ate through gas - like down to about 5 mpg. Also when it got to temperature it ran like crap. No damage though.

    The headers may have come with a coating that will smoke and burn off.
    Getting all that gunk in cylinders and valves isn't really a great idea. It will burn off, but can use some help from an extra shot of gas treatment like STP. But it shouldn't do any permanent damage.

    Depending on the car, it may refuse to run without an O2 sensor.
    "The internet is a place where absolutely nothing happens. You need to take advantage of that." ~ Strong Bad

  8. #8
    is as Gurgus does. Gurgus's Avatar
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    I thought that if you ran without an O2 sensor the ecu would run in a closed loop? At least, this is what my truck did when the sensor died on me.

  9. #9
    Footballus vita est iamlucky13's Avatar
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    That would actually be an open loop. It removes that source of feedback. A closed loop as feedback, and open loop doesn't.

    I think it depends on the ECU. It can just default to some profile, but I've got a suspicion that at least California certified vehicles won't run without it. Somebody else might know more.


    Oh just saw the note about the hot headers. This might be normal. New headers will temper. However, without the O2 sensor, you're probably not getting an optimum mix, so some combustion may still be happening in the exhaust. The engine we tuned for our senior design project actually had the headers glowing visibly with the lights on at one point. That's not ideal.
    "The internet is a place where absolutely nothing happens. You need to take advantage of that." ~ Strong Bad

  10. #10
    Senior Member Ziemas's Avatar
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    I ran with a deal 02 sensor for a few years in my Golf I..........

  11. #11
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    I live in California and several years ago (on a previous car), I removed my catalytic converter and ran a straight pipe. The car was an OBDII car so the second O2 sensor was not being used. The check engine light came on but the car ran fine.

  12. #12
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    The on-board computer will compensate for the missing sensor......your car will most
    likely run fine but less efficiently. Oh, and your check engine light will bug the crap out
    of you.

  13. #13
    MTN Bikin'
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    You'll be fine for a 21-mile trip. O2 sensors crap out ever once in a while, which makes the car run like there isn't one there. The worst that will happen is your gas mileage might change and you'll most likely get a CEL.

    Also, don't run a bottle of that cheap ass STP (or the like) crap. If you ever feel that you need to run something through the engine to clean it out look into SeaFoam. It's the only additive worth using when it's used properly.

  14. #14
    J E R S E Y S B E S T Jerseysbest's Avatar
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    It'll be fine, just don't make it a habit.
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    Cheating: a symptom of the problem.

  15. #15
    la vache fantôme phantomcow2's Avatar
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    Thanks.
    I'm at work now, all seemed fine. I don't smell that burning scent any more, which I believe is because the original manufacturing oil and grease is burnt off. I didn't clean these, and got crap on them while I was handling them with dirty hands.

    I'll have to do a rather bizarre routing. The original O2 sensor mounting was right on the exhaust manifold, this one is literally under the car (with the O2 sensor facing away from the ground). How should I join these wires together?
    Solder the ends and use heat shrink?
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  16. #16
    Non Tribuo Anus Rodentum and off to the next adventure (RIP) Stacey's Avatar
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    Is there any other method?

  17. #17
    la vache fantôme phantomcow2's Avatar
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    Oh yea, two of the four wires were black. Are these both ground? So it doesn't matter which way I wire it?
    C://dos
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  18. #18
    Senior Member Michigander's Avatar
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    Quote Originally Posted by iamlucky13 View Post
    I think it depends on the ECU. It can just default to some profile, but I've got a suspicion that at least California certified vehicles won't run without it.
    Yayyyy for Megasquirt!!!
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  19. #19
    MTN Bikin'
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    Quote Originally Posted by Michigander View Post
    Yayyyy for Megasquirt!!!
    Do you drive a VW?

    I ask because MS is way popular in the VW world. I'm not sure if it's as popular for any other makes though.

  20. #20
    Senior Member DannoXYZ's Avatar
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    Running without the O2 sensor connected will typically throw error-codes out the computer. It'll also typically richen the mixture slightly to be on the safe side, so your fuel-economy will go down the tubes.

    Also you CANNOT solder a longer wire onto the O2-sensor. Crimping is the only safe way to maintain a clean signal. That's because the sensor uses atmospheric air as a reference for the sensor and this air is obtained through the air-space inside the wires. If you solder one of the ends, it'll block this airway and the sensor won't be able to sample atm air. So use some butt-splices and crimps to attach a longer wire.
    Last edited by DannoXYZ; 08-10-07 at 04:53 PM.

  21. #21
    park ranger
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    what kind of car do you have OP.

    headers can glow if the timing is a little ********, the fuel mix will be burning longer than normal as it is pushed out of the cylinder. also your exhaust temps will vary depending on what your fuel mixture is, leaner burns hotter. monitoring exh. temp. is how some people like to tune their (race) cars.

    running without an o2 sensor probably won't be bad for it. it might idle rough, run fine, or flat out run bad...depends on how the ECU is setup.
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  22. #22
    Sleeper JeeperTim's Avatar
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    Crimping is not a good way to do it. You create a dissimular metal junction which will give a false reading. If you do crimp - use the kind that looks sort of like a wire nut so the wires twist together and then you crimp it over them.
    You are probably going to use a different metal wire to extend it though.... so the problem will still be there. It will probably run OK, but not optimum. Dig around in the wire loom a little - many have extra wire length tucked away for the O2 sensor.
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  23. #23
    la vache fantôme phantomcow2's Avatar
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    Okay so how about I use aluminum wire (which is what was originally used) to extend it. I will twist the ends together, and then heat shrink over it.
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  24. #24
    Senior Member DannoXYZ's Avatar
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    The original wire for the O2-sensor shouldn't be aluminium, it's stainless steel. Check out the last couple paragraphs on page-2 from this Bosch document on O2-sensors.pdf.
    Last edited by DannoXYZ; 08-10-07 at 05:14 PM.

  25. #25
    la vache fantôme phantomcow2's Avatar
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    THat doesn't make any sense at all. Insulated wire cannot take a sample of air for reference. I always thought O2 sensors have some electrochemical reaction which produces electricity when exposed to oxygen or something like htat. But hte wires should only be to carry the voltage.
    Either way, I got myself some 14ga stranded wire. I figure I'd like to induce the least amount of resistance as possible.
    I won't solder it, I'll twist the ends and heat shrink it instead.
    C://dos
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