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O2 readings 900

posted by  jerryc on  Sun Oct 24 08:08 CST 2010
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last visit: Wed Oct 8 21:28 CST 2014
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940T, 265k. Starts quickly, runs strong, has recently developed a lumpy idle only after warmup, and the tailpipe shows a lot of carbon. Mileage is not what I want. 18.5-19.5 in mixed driving, which is what the fed mileage site says, but is far lower than many claim. Anyway, I have no record of the 02 sensor ever being changed,
The question is related to, how to read O2 numbers with DVM. A friend and I read the sweep of the numbers, which run from abt .1 to a high of .82, over several readings per second. That is, the scale gives several numbers in a range over a short time, but they are not the same number range. Now what I want to know is, are we seeing the actual low and high, or is the low and high as though on an oscilloscope, and we are seeing points on that curve so the actual high may not be appearing on the DVM readout unless it coincides just at the right time.
Corollary, will a (in this case small cheap but working) analog VM needle read differently/better?







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    O2 readings 900

    posted by  mcduck on  Sun Oct 24 08:38 CST 2010
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    last visit: Sun Sep 9 11:47 CST 2012
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    Ananlog meters won't work; the input impedance is too low.
    I use a DVM with high/low recording, so over a couple of minites I get a fair idea.
    I also have a USB 'scope for my laptop.
    http://www.parallax.com/Store/Microcontrollers/BASICStampProgrammingKits/tabid/136/ProductID/46/List/1/Default.aspx?SortField=ProductName,ProductName








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      O2 readings 900

      posted by  jerryc on  Sun Oct 24 10:21 CST 2010
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      last visit: Wed Oct 8 21:28 CST 2014
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      "over a couple of minutes I get a fair idea..." So then I guess I was correct, but as you say over some time you get an idea. Good to understand, now is the .82 high enough.
      I was just looking at some other of your posts about O2 sensors, and soldering/crimping debate. You said on one that, I think it was the Mustang one, you have used many times. One of those has a short wire, another has a longer wire. Is the crimping best done on the bench after removing the old one, and then reinstall? if so, then the short wire one is the least expensive. If it can only be done on the car then for room to work, the longer wire seems it'd be easier to work with.
      I have been looking at some parts sites and it is very confusing, that so many are listed as 'correct fit' for all models 940, but on the same page others are listed as only fitting a certain model, or CA/non-CA, which would contradict the idea of the 'universal' ones.








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        O2 readings 900

        posted by  mcduck on  Sun Oct 24 11:47 CST 2010
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        last visit: Sun Sep 9 11:47 CST 2012
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        I use the Bosch 13953, from a '90 Ecort, which has short leads. It's generally less than $40 at the local Kragens.
        It's much easier to crimp the connections on the bench.
        I also use waterproof crimps that have heat shrink insulation.








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          O2 readings 900

          posted by  jerryc on  Mon Oct 25 20:52 CST 2010
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          last visit: Wed Oct 8 21:28 CST 2014
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          I checked one out, it's listed as you say. It does not come with those connectors and Kragen didn't have any, so when I find some (electronics store I think) I'm going to go that way, Thanks!







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