m20b27 stutter at WOT

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  • Syncro325is
    E30 Addict
    • Mar 2009
    • 574

    #1

    m20b27 stutter at WOT

    Customer asked me to swap a running motor into his 86 325e due to some sort of prior engine failure. He gave me the car not running and half apart unfortunately. Swapped new engine in and I now have a running issue where the car will idle high and will sputter to the point of no power at WOT with no load. I can pull the temp sensor and it will run all the way up to WOT with no sputter which seems to have the most effect on the running issue. I have checked resistance on the sensor and replaced it with a new one of similar resistance change. I have checked continuity between the wiring and the ICM as well as ECU. I have grounded everything.

    I have found multiple threads where people have seemed to have this same issue but the only solution I have found was using a potentiometer in place of the temp sensor to fool it into at least running, but still a little rich.

    It may also be helpful to know that when the sensor is plugged in I can clog the intake with my hand and get the car to run somewhat normal.

    I have smoke tested and eliminated any leaks.

    Any helpful suggestions for the temp sensor issue?
    sigpic
  • Kershaw
    R3V OG
    • Feb 2010
    • 11822

    #2
    Have you checked the CPS?
    Unplugged the o2 sensor?
    AWD > RWD

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    • Syncro325is
      E30 Addict
      • Mar 2009
      • 574

      #3
      Yes, Unplugged the o2 and it made no difference. Crank sensor in trans seems to be ok. It shuts off completely when the running ref sensor is unplugged. I did not find a chance to check resistance on the sensor yet
      sigpic

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      • TobyB
        R3V Elite
        • Oct 2011
        • 5163

        #4
        AFM?

        t
        now, sometimes I just mess with people. It's more entertaining that way. george graves

        Comment

        • Kershaw
          R3V OG
          • Feb 2010
          • 11822

          #5
          Originally posted by Syncro325is
          Yes, Unplugged the o2 and it made no difference. Crank sensor in trans seems to be ok. It shuts off completely when the running ref sensor is unplugged. I did not find a chance to check resistance on the sensor yet
          I would check the resistance, but I wouldn't even trust it if it reads 5500 -/+ 10%. I've seen way out of spec CPSs work just fine and ones that spec out ok be the issue.
          AWD > RWD

          Comment

          • Syncro325is
            E30 Addict
            • Mar 2009
            • 574

            #6
            Originally posted by Kershaw
            I would check the resistance, but I wouldn't even trust it if it reads 5500 -/+ 10%. I've seen way out of spec CPSs work just fine and ones that spec out ok be the issue.
            Haha gotta love pre obd2. Alrighty I believe I have a new sensor on the way anyway
            sigpic

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            • jeffnhiscars
              R3V OG
              • Jun 2011
              • 6010

              #7
              Have you checked the tps for continuity at idle and wot ?
              Seat Shocks....I have passed the baton to John Christy from Ninestitch. Email John or Garrett at ninestitch1@gmail.com

              https://www.r3vlimited.com/board/sho...86#post4944786
              Alice the Time Capsule
              http://www.r3vlimited.com/board/showthread.php?t=360504
              87 Zinno Cabrio barn find 98k and still smells like a barn. Build thread http://www.r3vlimited.com/board/show...20#post3455220

              Comment

              • TobyB
                R3V Elite
                • Oct 2011
                • 5163

                #8
                ...and fuel pressure?...

                t
                now, sometimes I just mess with people. It's more entertaining that way. george graves

                Comment

                • Syncro325is
                  E30 Addict
                  • Mar 2009
                  • 574

                  #9
                  Tps has been tested, and yes works perfectly. Fuel pressure is steady at 36 until it stutters at which point it is at 40 lbs.
                  sigpic

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