87 n/a limp mode?

  • #1

    87 n/a limp mode?

    Taking Z-Bum's advice, I have re-posted my thread changing the title to reflect what I think is
    the problem. I have combined the answers from my other thread so it should all be on this page. Admins please delete my thread "87 n/a reaching out (long)"

    Trying my damnedest to bring an 87 n/a back to life and she is fighting me every step of the way. So here is what I've done and what I am up against. Before I do this, I would like to apologize to anyone with an 87 that I told to check codes on the ECU. I have tried and I must be a tard, because I can not make heads or tails of the Haynes or FSM steps.
    Issue:
    Rev the engine and it will rev up. Let it drop a bit and it, now. revs right back up. After about 5 minutes, she will rev but not hold. If I rev the engine up to 4k rpms and hold it, the rpms drop off back to around idle. http://s58.photobucket.com/albums/g270/ … 1d8f9c.mp4
    Unplugged the AFM and she will not rev at all and dies. I have searched a little and I have read Xenon's list off sensor common symptoms.
    What I've done done:
    New plugs.
    New wires.
    New distributor.
    New rotor button.
    New CHTS & harness.
    New t-belt & water pump.
    Swapped the injector rail and injectors from a known running Z.
    Cat and exhaust from a running Z.
    Swapped CAS from a known working car ( small improvement).
    Tested a known good ECU (no change).
    Changed the 02 and the Z ran great for 10 minutes and back to what I think is "limp" mode.
    Fuel pressure:
    Cold = 28 @ idle & 37-38 @ hard rev.
    Hot = 22-24 @ idle & 30 @ hard rev.
    Could this be fuel pump?
    No fuel out of the fuel pressure regulator.
    The car has idle controls still.
    Per the door tag the car was manufactured 10/86. This would make sense that it might have an 86 motor, correct? How would this effect the 87 ECU?
    "zetto sun-ichi" group"
  • #2
    update of sorts:
    I went through the FSM again and found the fuel pressure reading and test. :livre Will be testing it tonight. Any additions are welcome. :banghead
    "zetto sun-ichi" group"
  • #3
    As far as I can tell the FPR failed the 2nd reading as you apply a vacuum to the system. I swapped it out with an FPR I got from the parts yard, there was no change in the test or performance. Fuel pressure checks out per the FSM. Anyone have any thoughts as to what could be causing the rpm's drop off once it warms up? There is no power on the low end. Last time I drove it and it started to act up, I opened the throttle up and the Z spit, sputtered coughed and then it took off.
    I am putting as much info in this hoping someone can hit on something I might be missing.
    "zetto sun-ichi" group"
  • #4
    Change the FPR anyways from another Z.

    Try swapping out the MAF from another running Z.

    Also, how is the gas? Old, stinky, dark, etc.?

    1986 300ZX Turbo…sold
    1990 Skyline GT-R…new money pit
    2014 Juke Nismo RS 6-speed…daily
  • #5
    Damn it. I missed that one in my write up. I have tested a MAF from a known working Z.
    The FPR, man I will try, but those things do not come off or go back on easy! O
    As for the gas, unsure. It was pretty low when I got the Z a year ago. I put in 5 gallons of fresh gas not to long ago.
    "zetto sun-ichi" group"
  • #6
    Update:
    Ok so I am in the process of testing the TCU.

    I spoke to the previous owner and he says he did swap the motor. Best I can tell this is an 86 motor. My question now is, would an 87 ecu matter with an 86 motor? Like I stated above the manufacture date on the door tag is 10/86. The body is definitely an 87. All the sensors are connected and there are not any just hanging about.

    Thoughts?
    "zetto sun-ichi" group"
  • #7
    Update:
    Well on a whem, plugged in an 86 ECU to go with what I found out to be an 86 engine. So far - so good! Keep your fingers crossed. I have to get this thing to pass an emissions test, just one time. Need the test to get the tag and this year is the last year 87's need it.
    "zetto sun-ichi" group"
  • #8
    Did you ever test the TPS?
  • #9
    The TPS is set "dead on" per the manual. I think the ECU did it. I will be doing some follow up tests. One of which will include putting the 87 ECU back, yes I said putting it back. I want to be able to put the problem back in the car and then see if it goes away by putting the 86 ECU back in again.
    "zetto sun-ichi" group"
  • #10
    re-visit/update:
    Forgot about this thread. Fixed the problem. 87Z w/ an 86 motor & an 87 ECU = limp mode.
    Swapped the ECU for an 86 and voilà problem solved. :-D
    "zetto sun-ichi" group"