Z32 Missfire possible ptu issue

Discussion in 'Technical' started by zedkelly, Jun 10, 2019.

  1. zedkelly

    zedkelly Member

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    Hey hows things?

    Got an 1990 na
    I'm just wondering if posible missfire issues on one Cylinder could be a PTU issue.

    -compression is fine on that cylinder
    -injector looks to be working
    -seems to be getting some sort of power on the coil plug

    Thanks
     
  2. rob260

    rob260 Moderator Staff Member

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    If you are missing spark the PTU is a possibility. If you have a logic probe you can test pulse signal to verify.

    Where are you located?
     
    Last edited: Jun 10, 2019
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  3. zedkelly

    zedkelly Member

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    I'm in Sydney . I Guess i would need a logic probé? I tested with a multimeter but maybe thats not enough right
     
  4. zedkelly

    zedkelly Member

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    Is there any way to specifically test the PTU
     
  5. IB

    IB ?????

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    ECU usually throws a code 21 when PTU drops a cylinder.
    See tech section for how to do an ECU diagnostic.
     
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  6. zedkelly

    zedkelly Member

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    Oh cool thanks Will do
     
  7. ZcrazyZx

    ZcrazyZx New Member

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    Its common on old style PTU's and usually wont throw an error code, if you've got a series 2 PTU then its pretty unlikely to be the problem, here's a diagram on testing it to be sure. Have you ohm tested the injector on this cylinder? Also pull your fuel pump fuse and ground the coil/plug while cranking to verify spark.
    EDIT: Here's a link to the post, the picture's clearer than mine https://forums.nicoclub.com/dead-cylinder-can-t-figure-out-why-read-me-s2-ptu-test-t564452.html
     

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  8. rob260

    rob260 Moderator Staff Member

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    A multi meter is too slow to catch a pulse signal.

    If you want to bring it up Hornsby way I’m pretty confident I could a diagnosis for you.
     
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  9. zedkelly

    zedkelly Member

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    hello peeps

    was having trouble logging in but now fixed thanks to rob
     
  10. zedkelly

    zedkelly Member

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    tried to start the car today, and first crank going well at full power, still didnt start, so I tried again, and nothing

    fuel pump is priming, no clicking relays nothing, what could this be now?
     
  11. zedkelly

    zedkelly Member

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    Hey everyone. So the car starts. I went under there and the whole starter broke off. The person before me decided to only use one Bolt to hold the starter on

    Anyway it's still missing on the same cylinder. I tried another s1 ptu. Tomor i'm going to try a spare S2 ptu.
     
  12. IB

    IB ?????

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    Do you know which cylinder is missing? If it's no 6, make sure that the correct connector is connected to the coil pack. It is possible to plug a different connector (I think vvt from memory).
     
  13. zedkelly

    zedkelly Member

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    It's the drivers side furthest to the front. Not sure what number that is?
     
  14. zx299

    zx299 Well-Known Member

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  15. zedkelly

    zedkelly Member

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    So new ptu still missing. How would i ohm test the injector?
     
  16. zedkelly

    zedkelly Member

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    Ok so injector is reading 13ohms
     
  17. rob260

    rob260 Moderator Staff Member

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    If you have spark on that cylinder then the problem is not the PTU.

    You also need fuel and compression to fire.

    Put a screwdriver on the injector while the car is running and use that to listen to see if it ticks.

    Do a compression test also.
     
  18. Blue300

    Blue300 New Member

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    Hi zedkelly.

    How many kms has the car done
    13 ohms seems to be fine, i get 12.5 ohms on all 6 of my injectors.

    Disconnect the fuel pump fuse and unplug injectors, pull the coil pack and spark plug out and test the plug is geting spark by leaving it connected to the coil and earthing the plug, it could be sparking before the tip if the plug is fouled.

    Also check the resistance of the driver side o2 sensor, if you can pull it out test that its working correctly by leaving it in open air it should read low voltage then submit it somewhere there is no oxygen and voltage should increase if its working correctly. If not then it will be telling the ecu to inject more fuel because it thinks its running lean due too much oxygen and could be fouling the plug or even setting off the timing by detecting knock sensor activity

    Test the ohms on the coolant temp sensor also because if this is faulty then it will tell the ecu the engine is at a particular temperature that it is not therfore warmer temperature has less oxygen so needs less fuel, and cooler temps have more o2 so need more fuel.

    I would also check the AFM make sure the hotwire isn't built up with gunk.

    These cars are pretty old now and after a while things build up with alot of greasy oils, even if the coolant hasn't been flushed when it should have been the anti rust inhibitors would now be non existent causing corrosion especially on the coolant temp sensor.

    All the best
     
  19. zedkelly

    zedkelly Member

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    Ok thanks guys. Ive narrowed it down. There is spark it seems when i grounded the plug. Also the injector definately is not ticking. Though it's strange becuase it's a replacement injector.
    Would o2 sensor and the like affect it?
     
  20. rob260

    rob260 Moderator Staff Member

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    No.

    Either a wiring fault or an fuel injector fault.

    Why did you replace it previously? Was it a new fuel injector? Were any tests carried out to verify that the fuel injector was operational before fitting it to the vehicle?
     

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