Can KV Histographs indicate ignition module issue?

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  • Witsend
    Banned
    • Nov 2012
    • 2942

    #16
    What did you find for the code 44 and the code 45-?? The numbers 127 and 124 are less than 1% from base programming.
    Crusty , sorry I missed the question .There were no codes (other than ones I caused messing with disconnecting MAF, and the ignition module, compression checking . Other than 4 cylinders low (120 psi and other 2 first tested at 150) it had just a less than satisfactory idle quality with nasty exhaust fumes. I never thought to actually look under the car to verify if the Catalytic Converter was missing or not. I'm so used to working on OBD2 with Cat Monitoring ,trims displayed in percentiles. I often won't look unless there is a P0420,P0430 code, leaks, rattles or exhaust restriction, or I'm doing something else under the car and I see it.
    The Customer told me his Cat converter was cut off and stolen while the car was parked overnight, and he just had a pipe welded in between for the interim because they only test 96 and up cars in this area. Because the Cat converter was missing , less pent up exhaust heat to keep that single wire O2 working at an optimum operating temperature at idle to respond to mixture changes as quick as it is designed to do. Sometimes I don't respond as quick as I should either when I have more than .1% Ethanol in me and also been told my tailpipe emissions are pretty obnoxious.
    Last edited by Witsend; 11-02-2014, 11:27 AM.

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    • Crusty
      Senior Member
      • Dec 2007
      • 2450

      #17
      Hi Witsend.
      Those vanes on the back of the balancer are different opening number of degrees, 10, 20, 30 (degrees of opening) so the ECM knows the crankshaft position and the other smaller evenly spaced notches are for a finer crankshaft speed resolution for the ECM. If the vanes are bent the sensor won't get an even input signal and setting the initial clearance so neither of the two sensors get whacked is fairly simple as long as the vanes on the back of the balancer are not bent. Seen a lot of damaged sensors over the years.

      I'm not sure I'd put a lot of faith in the stolen cat story. I would bet with all the other work it needed to make things run it had some soft coal stuffed through the injector system and that pooched the cat. I would bet it is still getting soft coal put into the tank instead of Top-Tier gasoline.

      The 3.0 GM engines always had a poor idle quality and when they transitioned to the "00" series (like the 3300) they didn't improve at all. The 3.8 made the transition to the 3800 (with the balance shaft) a lot better.

      The code charts for the two codes I mentioned are for too rich or too lean. What's todays' codes-?? P0171 and P0172-??

      Put a labscope on the O2 sensor and make sure it is capable of transitioning above 900mv and below 100mv quickly, as in less than 100ms once it gets a sudden squirt of added fuel or a sudden vacuum leak (both very momentary).

      Even with the cat missing, they don't usually make your eyes sting when things are completing the combustion properly. With 120 on 4 cylinders and 150 on 2 cylinders, and the 3300 engine design, I wouldn't even bother with idle roughness, just concentrate on the stinging eyes.
      Take a look at the short term fuel trim and the long term fuel trim in the 16 different block-learn cells under various engine loads and speeds for a better overall fuel delivery. Above 145 (from 128) or below about 105 (from 128) isn't what I would consider acceptable. The single wire oxygen sensors don't work very well relying on old rusty exhaust pipes for the ground circuit either. (that's why EVERY manufacturer started going to 2-wire, 3-wire and 4-wire O2 sensors years ago)

      Too much of that ethanol isn't helping either. 10% in regular fuel, 5% in midgrade and none (apparently) in Premium fuels. Most engines will react better with the premiums because they can get as much spark advance as they are capable of because the pizo-electric knock sensors not picking up and frequency.

      Up here the "Signature Can" in the corner of your pics would have 5% and 6% ........ Sleeman Honey Brown has a clean full flavour but it doesn't burn well in the car engines...LOL

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      • Witsend
        Banned
        • Nov 2012
        • 2942

        #18
        I thought the early single wire O2s generate their own voltage from only the precious metal of O2 interacting with hot gases and the PCM side of it did the calculating and any grounding side of the equation if any required at all. I can remember testing O2 circuits on feedback carburetor days by literally watching the Old Chrysler DRB box numbers changing from zero to one by holding the single wire with one hand and touching the positive battery terminal with the other hand and the zero would change to one if you had a non shorted good circuit. I really don't miss those cars, LOL... well I'm kinda rusty on some basics because The exhaust pipe actually does serve as the ground for single wire sensors, so I can understand why manufacturers decided to run 2 wires. I wonder if I could just retrofit a 2 wire sensor and just run the second wire to a bolt on the intake manifold instead of relying on a rusty exhaust pipe attached to a rusty exhaust manifold for reliable ground. You would think if the sensor was grounded at the pipe , how would any of voltage generated by the O2 sensor element ever be able to reach the PCM ? Must have a built in resistance so some of the generated voltage can back fed up the single wire and be read by the PCM.
        Last edited by Witsend; 11-02-2014, 06:11 PM.

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        • Crusty
          Senior Member
          • Dec 2007
          • 2450

          #19
          I never got 100% on the operation of the oxygen sensors other than to know that the grounding did affect things. We used to "play" with the O2 sensor signals by tapping in a 1.5-V AA battery but dammed if I can remember how right this minute.
          Always learning things, and usually RE-LEARNING the old school fundamentals....LOL
          If the threads are making good contact then just use a small self tapping screw and add a ground from right beside the sensor to the engine block and see what happens to the O2 sensor signal. Scope it before you add the "ground" and then scope it after you add the "ground".
          There is some sort of relationship to the threaded ground and the metal acting something like a capacitor for the sensor signal which can affect the sensor and possibly the "bias" of the sensor.
          The ECM may be doing exactly what it's supposed to do given that the O2 isn't functioning within the original design using the full exhaust system as a complete ground.
          I just remember that it can make a difference in "extreme" cases (adding the ground).
          It's all about electrons..... them little things that somehow are supposed to be "different" in a Euro-Turd.....ROFLMAO......
          I still say the molecules in the SLEEMAN are better than in the MILLER....LOL

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          • Witsend
            Banned
            • Nov 2012
            • 2942

            #20
            Sleeman? Never heard of it. Have to try it , but I'll have to Google it before I Guzzle it.

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            • bughood
              Junior Member
              • Aug 2012
              • 22

              #21
              I`d be looking real hard at the MAF. Nearly every time the airflow in grams is less than the litre of the engines displacement there is either a problem with the MAF or an unmetered air leak. Happy Thanksgiving

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