horrible s50 idle, please read, I am sick of this

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  • gregslow318i
    E30 Mastermind
    • Sep 2007
    • 1918

    #16
    o2 sensor? what about coolant temp? how new are they? also fuel injectors/ fuel filter?
    looking for a e30m50 swap harness adapter pm me $150 shipped
    email nitroman12@gmail.com

    Comment

    • BMW_TUNER
      E30 Fanatic
      • Jul 2006
      • 1377

      #17
      Any chance that there is a fault in the wiring to the alternator/starter. It may be load cycle that you are getting due to an intermitent loss of continuity at the alternator.
      1989 332IS -S-Fiddy Four-Some weight removed.
      5 lug E36 M3 Brakes Coilovers and LTW's and No ABS.

      Comment

      • sharky
        R3VLimited
        • Jan 2005
        • 2672

        #18
        is your throttle cable adjusted correctly, you will get a rpm surge and drop from that.

        Comment

        • Farbin Kaiber
          Lil' Puppet
          • Jul 2007
          • 29502

          #19
          Can you test another DME? Is there anyone that could help you with testing another set of sensors from a known working engine setup?

          Comment

          • VacMan
            R3VLimited
            • Apr 2007
            • 2405

            #20
            Agree with Farbin. I'd be swapping in another DME if you're 100% certain you have no vacuum leaks.


            1987 E30 cabrio | Bumper swap | H&R Sport | Koni Yellow | Eibach Sways | BavAuto strut bar | Cardinal seats
            MTech2 wheel | Husco Armrest | Smoked Hella Smileys | 5k HID | Stromung | RS003
            | Shadowline | Amber Fogs | Too much else to list



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            • Farbin Kaiber
              Lil' Puppet
              • Jul 2007
              • 29502

              #21
              Originally posted by VacMan
              Agree with Farbin. I'd be swapping in another DME if you're 100% certain you have no vacuum leaks.

              And, you are sure that way back in the beginning that ICV you installed is in known, good working order. And not backwards.

              Comment

              • Bimmer335is
                Advanced Member
                • Jun 2006
                • 146

                #22
                Check your Brake Booster as well for any leaks, that's where I found mine. I also had a bad DME. So check the both of those.

                Comment

                • Jason89i
                  E30 Modder
                  • Sep 2004
                  • 875

                  #23
                  its hard to diagnose over the internet without any knows / unknowns ruled out. need more hard data.

                  how much vacuume are you pulling? go buy a vacuume gauge and test at idle.
                  after clearing codes, do you still get "A1" ?
                  is there any slack in your t-body?
                  does your throttle plate return to set screw naturally?

                  cheers, jason

                  Comment

                  • rede30
                    R3V Elite
                    • Dec 2003
                    • 4697

                    #24
                    I finally spent some time on this. I grabbed the nuked wire harness and traced the melted wires and saw where they went and what they touched. I saw that a ground wire had melted in a spot where the green wire touched it and that ground wire grounded the TPS, intake air temp sensor, and the engine coolant temp sensor. I am not that great with how wiring works but I feel like when I had a wire melt in my harness, if a ground wire got power it would do damage to the sensors. So I ordered the three new sensors that got powah to their ground.

                    my tps did check out when I tested it with teh bentley tests. I have not checked my Intake Air sensor, it was only $20 for a new one. Can a bad TPS or Air intake sensor cause a surging idle?
                    Last edited by rede30; 04-05-2010, 03:03 PM.
                    https://www.youtube.com/channel/UC-h...wE3UqwjjmaTrXg

                    Comment

                    • Farbin Kaiber
                      Lil' Puppet
                      • Jul 2007
                      • 29502

                      #25
                      Prolly not on the two sensors, prolly yes on the three.

                      Comment

                      • rede30
                        R3V Elite
                        • Dec 2003
                        • 4697

                        #26
                        Originally posted by Farbin Kaiber
                        Prolly not on the two sensors, prolly yes on the three.
                        wait, what? do yo mean if all three are bad my idle might surge? Or that they all three would go bad if their ground got power?
                        https://www.youtube.com/channel/UC-h...wE3UqwjjmaTrXg

                        Comment

                        • Farbin Kaiber
                          Lil' Puppet
                          • Jul 2007
                          • 29502

                          #27
                          No, that the issue is more likely related to the three sensors you said you were replacing opposed to the two you asked about potential for causing issues. It may only be one of those three, but who knows without pulling them and testing them by the book.

                          Comment

                          • r4esh
                            E30 Addict
                            • Jan 2010
                            • 439

                            #28
                            With the intake off, go through the ETM test. Get a multimeter and test each sensor one by one... tedious, but it will eliminate the questions... did for me - i determined I had a failed cam sensor. Replaced it and she purred.
                            (oo=[][]=oo)
                            Web Design PNW

                            Comment

                            • Farbin Kaiber
                              Lil' Puppet
                              • Jul 2007
                              • 29502

                              #29
                              ^ He said he already ordered all three that were potentially fried via a ground short in the harness.

                              Comment

                              • sushipower
                                Advanced Member
                                • Aug 2005
                                • 156

                                #30
                                A bad TPS or Air intake sensor can cause rough idle. The question is what caused the short? Did you make sure "ALL" ground cables are connected (including the engine block)? Hope you find the cause.

                                Comment

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