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Engine misses for 5 seconds on cold start

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    Engine misses for 5 seconds on cold start

    This one has baffled me. On cold starts (after sitting overnight) the car spits and sputters for the first 3-6 seconds, and then clears up and idles smooth and on mark.

    Car didn't start doing this until a few weeks ago.

    Due to what gets used and what changes that fast, I don't think it's the O2 Sensor (not used until warm) or the Coolant sensor (Temp doesn't change in 3 seconds).

    I'd say I had leaky injectors that caused a few poor firings until the cylinders were clear, but there is no increased smell of gas, and the injectors are freshly cleaned and flow tested as of 7 months ago. It also doesn't have trouble starting up, maybe an extra crank, but nothing that causes even a split second fear that it won't start.

    Thoughts?
    -------------------------------------------------
    1989 - E30 - M20B25 - Manual. Approx 300,000+ miles - Track Rat & Weekend Fun
    2000 - E46 - M52TUB28 - Manual. Approx 130,000 miles - [not so] Daily Driver

    sigpic

    I'm looking for a Lachssilber Passenger Fender and Hood. PM if you have one or both to sell!

    #2
    What engine and motronic version?

    Comment


      #3
      Originally posted by Andy.B View Post
      What engine and motronic version?
      Whoops, I should probably state that more clearly :)

      M20B25
      Motronics 1.3
      173 ECU
      -------------------------------------------------
      1989 - E30 - M20B25 - Manual. Approx 300,000+ miles - Track Rat & Weekend Fun
      2000 - E46 - M52TUB28 - Manual. Approx 130,000 miles - [not so] Daily Driver

      sigpic

      I'm looking for a Lachssilber Passenger Fender and Hood. PM if you have one or both to sell!

      Comment


        #4
        The first thing that comes to mind after leaking injectors is coolant/oil leaking into cylinder from a bad hg or crack, very poor compression, or air leaks.

        Comment


          #5
          Originally posted by Andy.B View Post
          The first thing that comes to mind after leaking injectors is coolant/oil leaking into cylinder from a bad hg or crack, very poor compression, or air leaks.
          don't say that! :shock:

          That actually did cross my mind... but it's running so well and the HG is only 2 years old. No other signs of HG trouble either... of course that doesn't mean anything. I have been missing a little bit of coolant recently (longer than the start issue), but I also sprung a small leak from my waterpump and I was hoping that was where all the water vanishing too. I'm not blowing steam out the tail pipe yet either.

          An air leak would cause a poor idle, and wouldn't clear within a few seconds afaik. I think I can dismiss that one safely.

          I've never dealt with bad HG issues. If I pull a plug and shove a small cleaning brush into the cylinder will it come out wet/oily if that's the issue? I'm not sure how much of a leak it would take to cause an issue like this.
          -------------------------------------------------
          1989 - E30 - M20B25 - Manual. Approx 300,000+ miles - Track Rat & Weekend Fun
          2000 - E46 - M52TUB28 - Manual. Approx 130,000 miles - [not so] Daily Driver

          sigpic

          I'm looking for a Lachssilber Passenger Fender and Hood. PM if you have one or both to sell!

          Comment


            #6
            Got a friend with an e30? Try swapping in a different MAF. Maybe yours is gunked up.

            Comment


              #7
              Originally posted by russc View Post
              Got a friend with an e30? Try swapping in a different MAF. Maybe yours is gunked up.
              Also less likely, as my AFM (no MAF in these) is also freshly rebuilt as of a few months ago. I've never heard of an AFM fixing its self after a few seconds running either. Perhaps you or someone else has?
              -------------------------------------------------
              1989 - E30 - M20B25 - Manual. Approx 300,000+ miles - Track Rat & Weekend Fun
              2000 - E46 - M52TUB28 - Manual. Approx 130,000 miles - [not so] Daily Driver

              sigpic

              I'm looking for a Lachssilber Passenger Fender and Hood. PM if you have one or both to sell!

              Comment


                #8
                yeah, you know what...disregard that. That situation would start up fine, but then die after 5 seconds.

                Comment

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