Mystery Problem Limp Mode

  • #1

    Mystery Problem Limp Mode

    I've had a very annoying mystery problem with my 86 2+2 automatic thats been driving me nuts. The car constantly goes into limp mode. If I unplug the auto transmission module in the spare tire well the car will run great for one trip. Then if I turn the car off and let it sit, then turn it back on its back in limp mode again. The ecu gives me codes 23 and 31. I'm guessing the code 31 is because my air conditioner doesn't work. I think it must be some kind of electrical problem. My next step is to take multimeter to all the wiring harnesses starting with the two tps connectors.

    Here is a list of everything I suspected and replaced:

    New MAF sensor
    New TPS
    New ECU
    New Battery
    New PCV valve

    Along with a ton of other brand new parts that are unrelated.

    Any advice would be appreciated, this is my daily driver so its really a pain having it go into limp mode every day, and having to unplug that connector in the back again.
    I've tried my best to fix it, I even took it to a local mechanical who couldn't figure out the problem. And when I say limp mode it means it won't rev past the 2200-2500 rpms range.
    No matter what I try it still spits out that code 23.
    Proud Owner of an 86' 2+2

    XXR 526 17x9 Wheels
  • #2
    I'm thinking that new tps I bought is a dud. As you know the TPS on the automatics have a second grey connector. If I unplug that grey connector and try revving it, guess what happens…no limp mode! but with that connector unplugged the exhaust smells like its running real rich. So since this new tps has a lifetime warranty I'm going to take it back and try yet a 3rd new tps. Still would be interested in anyone elses take on this.
    Proud Owner of an 86' 2+2

    XXR 526 17x9 Wheels
  • #3
    Finally gave in and took it to a mechanic, they said the TPS is getting to much voltage and they're trying to figure out why. They should let me know sometime today and whether or not they can fix it. I'll post updates in case anyone else has this problem, cause I've been pulling my hair out trying to figure it out.
    Proud Owner of an 86' 2+2

    XXR 526 17x9 Wheels
  • #4
    The Automatic Transmission Control module located in the spare tire well failed/shorted out, that was the source of all my problems.
    Proud Owner of an 86' 2+2

    XXR 526 17x9 Wheels
  • #5
    He said the TPS is getting too much voltage because hes a n00b used to modern cars that run a 5v reference. The Z31 is 12v reference.
    - VG30DET (HE341) 86 300ZX - 1982 280ZX Turbo - Headered NA 1986 300ZX 2+2 - 2000 Xterra -