Z31 Possible ECU Fault

Discussion in 'Technical' started by iannbn3, Jan 24, 2022.

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  1. iannbn3

    iannbn3 New Member

    Hi Folks,
    I've got a 1987 300zx man turbo. I've had an ongoing problem with it just dying for no apparent reason - It seems to lose 1 cylinder and if you apply even just a small amount of accelerator -It stops altogether - The mechanics have had the injectors out and refurbished the (a year ago) and new plugs/point etc. It ran OK for a while but started to lose a cylinder every so often again.
    This time around the mechanic was from a racing background (so knew a few things ) He had all the wiring out from under the dash including the ECU - He also had gauge set up to check fuel pressure while test driving. The pressure regulator and control solenoid look to be running OK.
    Some follow up by myself seems to point to it possibly being an intermittent fault with the ECU.
    Any ideas would be greatly appreciated.
    Cheers... Ian_C
     
  2. NI85

    NI85 Active Member

    http://www.xenonzcar.com/z31/fsm.html Download FSMs if you haven't already done so.

    Then wipe any previous assumptions on what works or doesn't and start from scratch. As initial assumptions can be misleading.

    Run ecu codes and see what comes up. (Not everything has a code to trip.) The 88 FSM EFEC section gives a chart like diagnosis table and troubleshooting list of Issues and possible causes. Follow it to know what's working or not. EF-EC page 31 to 136

    Hope that helps.
     
    MickW likes this.
  3. MickW

    MickW Carntry member...

    Silly questions but is it a problem from soon after a cold start or after you've been driving for a while?
    And is it more prevalent on a hot day or a cold day?
    Reason I ask - sometimes an aged circuit board in a ECU might have some fractured or "dry" solder joins.
    Best way to test for that? I could tell you how to check a Z32 ECU on-the-fly with a tech savvy mate in the passenger seat. But I have NFI about the Z31 ECUs, sorry.

    Most members will tell you to swap the ECU and see what happens. If the Z31 ECUs are cheap enough, this is the best way to get an answer. Paying an electronics tech to troubleshoot an intermittent fault while the car is running?
    That would be an expensive challenge...
     
  4. iannbn3

    iannbn3 New Member


    Thanks Folks for your feedback - Unfortunately, the problem got a little worse (it wouldn't even start) and through a series of coincidences, I ended up selling it to someone who had all the workshop paraphenalia to do the in depth analysis needed. ( and the time and money !!) So, after 28 years, I have let the lady go to a new home !

    Cheers Ian_C
     
    MickW likes this.
  5. NI85

    NI85 Active Member

    If you keep in contact with whom you sold the car to. It would be nice to know what the problem was, once they've solved it.
     
    MickW likes this.
  6. MickW

    MickW Carntry member...

    Agreed. We do love a good diagnostic story.
     
  7. MickW

    MickW Carntry member...

    Well done! After 28 years together most ladies make you pay for their new home :)
     

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