Rough Idling/running & CEL after performance chip install (M42)

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  • BoxE30
    Member
    • Aug 2020
    • 72

    #1

    Rough Idling/running & CEL after performance chip install (M42)

    Hi guys,

    Long time lingerer/searcher on the forum. I had an issue arise for which there seems to be smaller/more specific potential fixes, but figured I'd put this one out there. Quick history: I purchased the car late last year with a rough idle and a bad profile gasket, having the job done by a good local shop here in San Diego not long after purchase. Since that job, the car has run fine, with just the slightest hesitation at startup, but give it some gas for a minute or two and it's fine.

    Yesterday, I installed a Turner Conforti performance chip and it immediately had very rough/shaking startup, with rich exhaust fumes, that seemed to get better when I kept giving it gas for a decent while. Once it leveled out and idled fine, I took it for a spin - nothing aggressive - just running it on streets with a small freeway distance. Came back, turned it off, and started it again. Seemed to start and idle alright when hot.

    I went ahead and put the stock chip back in just to see if the new chip was the problem. Started it when it cooled down for a while and seemed to have the same issue even with the stock chip this time around. I then went ahead and cleaned out the ICV, which was dirty, but wouldn't say filthy, and still has the same issue.

    Today, I put the Turner chip back in and it had the roughest start so far, even squealing the belts a bit. Kept on the gas for a decent while and it then threw a CEL and wouldn't even idle properly when heated up. Pretty concerned at this point that I may have damaged something. Any ideas?

    Thank you in advance!
    Sean
  • prisonerofdoom83
    E30 Addict
    • May 2013
    • 519

    #2
    Stomp test for the CEL?

    Comment

    • twright
      Mod Crazy
      • Sep 2008
      • 705

      #3
      My M42 acted like that when it wanted new ignition wires. Unfortunately, they are hard to test and expensive. I'd try everything else first.

      Comment

      • turner.e30
        Member
        • Aug 2020
        • 42

        #4
        I'm assuming you disconnected the battery before you installed the chips? The DME will "reset" when the battery is disconnected and will need some time to sort itself out. Does it clear up once you drive it for a bit?

        Comment

        • BoxE30
          Member
          • Aug 2020
          • 72

          #5
          Originally posted by turner.e30
          I'm assuming you disconnected the battery before you installed the chips? The DME will "reset" when the battery is disconnected and will need some time to sort itself out. Does it clear up once you drive it for a bit?
          Yes, battery disconnected. How long for it to reset itself?

          Comment

          • BoxE30
            Member
            • Aug 2020
            • 72

            #6
            Originally posted by prisonerofdoom83
            Stomp test for the CEL?
            Tried one yesterday but didn't get any feedback from the dash. I then found out this afternoon I needed to close the door (open since it was very hot yesterday). I'll give it another try tomorrow.

            Comment

            • turner.e30
              Member
              • Aug 2020
              • 42

              #7
              Originally posted by BoxE30

              Yes, battery disconnected. How long for it to reset itself?
              Shouldn’t be very long. A few times around the block should do it. If it doesn’t clear up pretty quickly then there might be an issue of a different kind.

              Comment

              • Codym42
                Mod Crazy
                • Mar 2013
                • 611

                #8
                Make sure to check this... https://www.r3vlimited.com/board/for...-this-wire-for
                '90 325i - 5 speed coupe
                '05 330ci 6MT ZHP

                Comment

                • BoxE30
                  Member
                  • Aug 2020
                  • 72

                  #9
                  Originally posted by Codym42
                  Glad you brought up. I checked and thankfully not connected. As for the CEL, I put a new (to me) DME in that hadn't been tampered with and the car runs fine again. Thinking I must've had static that I hadn't grounded properly when I got into the first DME. Getting a replacement Turner chip and seeing if it changes anything on either the first DME or the 2nd one.

                  Comment

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