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91 civic code 4 dohc zc

Discussion in 'ECU's, Electronics, and Tuning' started by a1953mdl, Sep 2, 2010.

  1. a1953mdl

    a1953mdl New Member

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    My son has a 91 civic that has had a dohc zc engine swapped in.
    The ecu is blinking code 4.
    I believe it is a 3rd gen dohc zc engine.
    The car is still obd0.
    The cam sensor (cyl/tdc) resistance measured 890 ohms ( suppose to be between 600 and 1,000), so that seems okay. Checked continuity between each wire and ground. one had 0 ohms and the other measured 890 ohms (same as reading across the two wires). So it would appear the cam sensor is bad, correct?
    Money is tight enough, don't want to just through cash at it.

    Should each of the two wires have zero resistance to ground?

    Symptoms
    starts and runs, but idles rough. Will rev (not smoothly/ struggles) to 3k or so but starts to backfire after 3k.
    The car has not run correctly since the engine was swapped in.
    We tried three different ecu in it.

    Lee
     
  2. a1953mdl

    a1953mdl New Member

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    Okay, If I re-read correctly, the wires from the sensor should NOT have continuity. This came from the trouble shooting flowchart for Code 9 on a dohc. I don't have a factory manual, so this is the closest I could find online. Both code 4 and 9 are for the same sensor.

    Anyway went ahead and bout a new sensor form the local O'Reillys. It did not change the problem. I had previously checked the wiring from the sensor to C1 and C2 and it checks fine.
    I have a PM6 ecu in it. I had read that this was good to use. I also tried a PR4 ecu (it was installed when he bought the car).
    Both run the same. Starts, Idles a little rough and will rev with a struggle to 3K and then start mis firing.
    It runs the same whether the sensor is plugged in or not??????????????????
    Any thoughts at all?
     
  3. a1953mdl

    a1953mdl New Member

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    I'm running out of things to check. I have switched the two green/striped wires in the sensor plug. No change, so swapped them back.
    Checked the cams timing and they checked correct.
    Triple checked the spark plug wiring order on the distributor and tried checking it with the 2 and 3 reversed anyway. It was right the first time.

    Any ideas????
    Lee
     
  4. Fernpatch

    Fernpatch Member

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    when you checked the wires for contenuity to ground were they plugged in at either end? I am thinking that the wire with 0ohms to ground is shorted somewhere. The wires added for the sensor, are they ground shielded, twisted pair, or just loose wires?
     
  5. a1953mdl

    a1953mdl New Member

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    When I checked continuity of the sensor it was not plugged into anything. As I read later, showing continuity WAS a sign of a problem (you are right, should not show 0 ohms). I did replace the sensor, but still same problem.
    The extensions added for the sensor are just similar wire to what was there, not shielded or twisted. Later in the harness they are shielded. The extension wires are soldered and shrink wrapped then have cable loom over that.

    Further update.
    I find on the internet that code 4, code 8 and code 9 are similar and the sensors related to each are often referred to by the same name.......but are different. I had been reading on a code 9 even though I was getting a code 4. It was the only troubleshooting flowchart I could find at the time and seemed to relate to the same sensor.
    Anyway, code 4 refers to the crank angle sensor in the distributor, not the sensors at the end of the ex. camshaft.
    I am in the process of checking this out and verifying proper ohms and ecu pin placement. AND straightening out several bad wire connections.

    Hopefully getting closer. Still open to ideas of things to check. I am coming to the conclusion that this car has been through a two owners during the swap. Some work is done very well.......other is pure sh!t. I am guessing the first owner did the sh!t work and couldn't get it to run, then the second owner did some good work trying to correct it, but gave up.
    What fun.

    Lee
     
  6. Fernpatch

    Fernpatch Member

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    Good luck with correcting the shit work done by the old owner. It will be worth it when you get it going right though.
     
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