Looking for some input on a poor running issue

  • #1

    Looking for some input on a poor running issue

    My car has a bit of a issue. It runs bad when cold but does not have a hard start. When I start the car in the morning it will fire right up and idle flawlessly and run fine for 30 seconds to a minute. Then out of nowhere the car will start to buck on light acceleration. When this bucking happens it will still idle fine and the bucking goes away under moderate to hard acceleration but has no power. Then after the engine warms up some (does not need to get all the way to operating temp) it will start to run normally again. There are no codes in the Ecu and I have replaced a lot of parts on the car recently as preventative maintenance not problem chasing. I was thinking that the new parts would have eliminated this concern due to the symptoms it has.

    The car is a 1984 300zx turbo with manual transmission
    Recently I replaced the
    Timing belt
    Front seals
    Water pump
    All the fluids
    Chts and sub harness
    Spark plugs
    Wires
    Cap
    Rotor
    Air filter
    Reset base idle and timing to spec
    Crank sensor (was throwing a code and had hot start issue)
    That is all I can think of for right now
    The recall was done to my car will it help to rewire the injectors back to the original layout?

    If any one has any suggestions let me know from the research I have been doing it looks like a lot of people have had this same problem and can not fix it or give up and live with it. I beleive this can be fixed and am curious to hear some input before I get knee deep into testing every single component until I ding a failure.
  • #2
    Try a different ECU.
    84-85 ECUs are the worst.
  • #3
    do you mean try another 84/85 or switch to a kouki Ecu and O2 sensor
  • #4
    Originally posted by V8srfun View Post
    do you mean try another 84/85 or switch to a kouki Ecu and O2 sensor

    Your call.

    I would go for another 84/85 turbo ECU or yes, go to a later ECU.
    You can only go up to 87 because of injectors. Not worth using dropping resistors.

    Please read the following
    http://www.redz31.net/pages/fuel.html
  • #5
    What does a z31 Ecu usually go for on the used market I was in to s13's for a couple years and there ecu's were like 50 bucks
  • #6
    Just saw one go for 100$ I have the 87 T ecu in my 85, and I wired the proper o2 and it all works flawlessly.
    http://z31performance.com/showthread…2-2-(-now-NA2T
    My build thread (:
  • #7
    $50-80 for ECUs 84-87
    I wouldn't pay anymore than that

    The 88-89's fetch a higher price.
  • #8
    On Saturday I reset the timing it was for some reason at 0deg so I put it up to factory spec of +20 defy and then cleared the old crank sensor code that I never erased after replacing the faulty one. The poor running must have been caused by the lack of timing advance and or the old code because the car is %100 now