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2.7i running rich after Mark D, bigger injectors

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    2.7i running rich after Mark D, bigger injectors

    Recently built a 2.7i with SETA pistons. I ran the bigger injectors with the stock chip for the first 800 miles, with no problems at all. Now I've finally obtained and installed a Mark D 17-19lb 93 oct 7k rpm chip and its running super rich. CEL is on all the time, and I've put about 75 miles on it already hoping it would work itself out.

    The injectors I'm using are 0 280 150 440 which are the purple "21.5lb" from a m52b28. Now before everyone says they are too big, I did my research and they actually flow the same or slightly less than 0 280 155 710 GenIII 19lb (ie mustang injectors) that many people are sucessfully running with this chip. So I really don't believe its the injectors.

    The question is, now that the Mark D chip is allowing a lot more fuel to be dumped in, what is it thats causing it not to run stoich. I didn't replace the O2 sensor or any ignition parts when I did the build, and I'm guessing those would be the first places to start. Any other ideas?
    Owned lots of E30's
    Currently sporting:
    85 324td
    86 535i
    89 635csi
    Feedback thread

    #2
    start with an o2 sensor, a coolant temp sensor, and a fresh set of plugs

    but I think those injectors are too big, try a set of 17.5#s from an m50
    1989 cirrisblau-metallic 325i

    Comment


      #3
      Thanks, the O2 sensor makes sense. I don't really understand how the coolant temp sensor would relate to a rich running situation.
      Owned lots of E30's
      Currently sporting:
      85 324td
      86 535i
      89 635csi
      Feedback thread

      Comment


        #4
        I honestly think you and me just got a bad chip. I've got a Mark D chip and 19 lb injectors and my CEL was constantly coming on at 2k. I put in a new AFM and O2 sensor and that fixed the CEL, but if I rev the engine up it still puffs out black smoke. It also failed smog.

        I also felt zero difference in power. Everyone with this combo says they felt a difference and it passes smog with flying colors.

        Matt
        Matt

        Originally posted by slammin.e28guy
        I pack my CD player with asbestos. Those mother fuckers pay dearly for stealing my shit.
        Originally posted by kronus
        try whacking parts of the motor with a wrench while yelling "YOU WANT SUMMA DIS? HUH?"
        Originally posted by chadthestampede
        This is like a reverse build thread; it starts out nice and gets shitty.

        Comment


          #5
          Originally posted by Jargo View Post
          Thanks, the O2 sensor makes sense. I don't really understand how the coolant temp sensor would relate to a rich running situation.
          the coolant temp sensor "tells" the DME how warm the engine is. The colder, it runns a little richer, once it warms up, a lot leaner. If the CTS has failed, it may send a faulty "cold" signal to the DME, and the DME will dump more fuel "thinking" the engine needs to warm up
          1989 cirrisblau-metallic 325i

          Comment


            #6
            Originally posted by SpecM View Post
            the coolant temp sensor "tells" the DME how warm the engine is. The colder, it runns a little richer, once it warms up, a lot leaner. If the CTS has failed, it may send a faulty "cold" signal to the DME, and the DME will dump more fuel "thinking" the engine needs to warm up
            Well now that makes perfect sense!

            I guess I will start with an O2 and CTS, and probably fresh wires and plugs just for good measure. It just sucks that it ran perfectly fine with the stock chip.
            Owned lots of E30's
            Currently sporting:
            85 324td
            86 535i
            89 635csi
            Feedback thread

            Comment


              #7
              After running tests on just about everything with my multimeter, I found that my throttle cable was adjusted too tight and wasn't allowing the throttle switch to fully close. Apparently that has quite an effect on idle quality. Since fixing that it has gotten much more driveable. However, I messed with the idle mixture screw on the AFM and now I've got it out of wack, so it'll take some adjusting to get it back to factory.
              Owned lots of E30's
              Currently sporting:
              85 324td
              86 535i
              89 635csi
              Feedback thread

              Comment


                #8
                Have you tried called Mark and mentioning your situation, he might have a suggestion/solution for your problem?

                Comment


                  #9
                  No, I'd be highly surprised if he has time to answer phone calls...I emailed once and never got a response.
                  Owned lots of E30's
                  Currently sporting:
                  85 324td
                  86 535i
                  89 635csi
                  Feedback thread

                  Comment


                    #10
                    Actually, I called him last Friday morning and he answered in a couple of rings. He said he had a really bad case of the flu so he was out of commission for the week. Emailed him this morning and he explained that his symptoms got worse (checking to see when my chip will arrive). Just keep trying as he will be glad to answer your questions when you get a hold of him.

                    Comment


                      #11
                      Interesting, I emailed him once about my problems and when I told him I got the chip in a group buy he just stopped responding.

                      Matt
                      Matt

                      Originally posted by slammin.e28guy
                      I pack my CD player with asbestos. Those mother fuckers pay dearly for stealing my shit.
                      Originally posted by kronus
                      try whacking parts of the motor with a wrench while yelling "YOU WANT SUMMA DIS? HUH?"
                      Originally posted by chadthestampede
                      This is like a reverse build thread; it starts out nice and gets shitty.

                      Comment

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