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Car runs on 2 cylinders when cold

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  • Car runs on 2 cylinders when cold

    Hi guys,

    A bit stuck with this problem on my S13 hatch (SR20) and looking for suggestions.
    In short, the car has no spark in cylinder 1 or cylinder 2 on cold start but when it warms up and reaches about 50 degrees C suddenly all 4 cylinders start firing and the car runs fine, its like someone just flicked a switch.

    I'm using LS2 truck coils , so I have removed the ignitor and bypassed it by wiring straight across.
    The car was running fine with this setup until a couple of weeks ago when this problem started.
    Once again when the car warms up it runs perfectly on all 4, this problem only happens when cold.

    So bearing in mind that this is a spark problem, here's what I know:
    - Replaced coil pack and tried a few other replacements, no difference - it is not a coil pack problem
    - The coil pack is getting 13.7V while running, even when cylinder 1 and 2 have no spark.
    - Ground pins (2 per coil) have continuity to their grounding points (I have triple checked these)
    - Coil signal wires for coil 1 and 2 are not receiving a signal from the ECU when not firing, but suddenly receive a good clear signal when it warms up enough (runs on all 4)
    - I've changed the CAS, no difference
    - Base timing is set correctly to 15 degrees
    - Coil signal wire has continuity from the coil to the ECU when it is running on 2 cylinders, and 4
    - Probing the coil signal wire directly as it comes out of the ECU shows no signal being sent from the ECU to coils 1 and 2 when it has this problem. Signal is still being sent as normal to coils 3 and 4.

    So at this stage it would seem it was an ECU problem, since the ECU isn't sending a signal. However I've tried a different ECU (standard ECU) and the car had the same problem.

    I am using a chipped standard S13 SR20DET ECU (JDM car so SR20 as standard) and have also tried another identical (non-chipped) standard ECU.

    So any ideas what would cause the ECU to not send a signal to the coil? I'm a bit stuck at this point and my next move would be to replace the entire engine loom, which I don't particularly want to do...

  • #2
    anyone?

    Comment


    • #3
      Try going back to an igniter and stock coils just to check? Or S15 coils which have a built-in igniter?
      '18 Chevrolet Volt - Electric fun hatch for DD duty!


      DefSport Koni Sleeve and Spring Perch Buy!!!
      http://www.nissanroadracing.com/showthread.php?t=5902

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      • #4
        Is the ECU kicking out any error codes?

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        • #5
          Def I've tried S15 coils, LS2 truck coils and now different coils. And same problem with all of them. No error codes.

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          • #6
            Check continuity of the wires when cold and see if any are broken or grounding out

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            • #7
              Originally posted by jfryjfry View Post
              Check continuity of the wires when cold and see if any are broken or grounding out
              Have done this with everything I thought could be relevant (CAS, coil pack signal and power wires). Any suggestions which wires I should check?

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              • #8
                You may want to try to disconnect the coilpack and see if the signal at the ecu appears. I would also take a look at the ecu output to ground resistance while its disconnected.

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                • #9
                  Check from ecu connector out to coil for continuity. Go from there.
                  '18 Chevrolet Volt - Electric fun hatch for DD duty!


                  DefSport Koni Sleeve and Spring Perch Buy!!!
                  http://www.nissanroadracing.com/showthread.php?t=5902

                  Comment


                  • #10
                    Originally posted by josh_s13 View Post
                    You may want to try to disconnect the coilpack and see if the signal at the ecu appears. I would also take a look at the ecu output to ground resistance while its disconnected.
                    Can't remember if I've checked this yet, will do.

                    Originally posted by Def View Post
                    Check from ecu connector out to coil for continuity. Go from there.
                    Yeah they all have continuity, I'm leaning more toward an earthing or CAS problem.

                    Comment


                    • #11
                      With minimal knowledge of the SR's ecu, i would think that if the CAS was failing bad enough to have the ecu fail to ignite 2 cylinders it would kick a code. I would wildly guess thar CAS failure would lead to the car not running at all or running in limp mode.

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                      • #12
                        I changed the whole engine loom and that seems to have fixed it. Couldn't find anything obvious wrong with the old loom. If I can be bothered I might have a better look through the old loom at some stage to try to figure out what it was.

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