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    2.7i Idle Surging

    I just but a 2.5 head off an 89 325i onto my 2.7 87 325 bottom end. Timing is perfect the only thing is that it seems to have an idle problem. When its running it will rev up than die down almost shutting off than it revs back up. Ive heard that the coolant sensor sometime causes these, the icv might be it, and or my maf. When I took it around the block to drive it jerks a lot and almost bucks. Anyone have any suggestions??????? I also dont have my O2 sensor in the pipe yet its sitting there because the old one is rust in and can't get it out. I also dont have a 2.5 canister on it could that be causing any of this?????

    #2
    I'd suspect an intake leak and/or a sticky ICV.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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      #3
      If your new o2 sensor is hanging and plugged in, pull it off and either plug in the stuck one, or leave it unplugged.
      sigpic

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        #4
        Which fuel injectors and ecu did you use?


        '89 325i - Totaled... good bye my love...
        '87 327i budget stroker - SOLD!!!
        '92 240sx - ca18det powered drift toy - SOLD!!!
        '89 325i - coupe - NEW daily
        '96 Audi A6 Quattro- Grocery getter/baby hauler
        '99 Busa - weekend wheelie monster

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          #5
          ecu and injectors are from the 89

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            #6
            post pics of your set up

            1986 325es (69k) Garage Queen Buy It Now 10k;1986 325es (track rat) 2.7i How-To & 1.1/1.3Motronic UpGrade
            1991 318is (daily driver) 1991 318is M42 Maintenance How-To;1989 325i (parts car)

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              #7
              Pics will be up tomorrow

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                #8
                Pics Are Up













                The sensors that arent hooked up on the thermo housing is because its the old 2.7 one and the 2.5 harness only needs the two that are plugged in.

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                  #9
                  most likely a dirty ICV or vac leak

                  otherwise, that "hot air intake" cone filter looks like it's been through a war. find a stock airbox and a new paper filter, you'll pick up an easy 5hp.
                  Build thread

                  Bimmerlabs

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                    #10
                    We did take the ICV out and it looked clean and we even cleaned it after that. Im going to see if I can borrow a good one to see if thats the problem. Any other suggestions??

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                      #11
                      ICV is fine. My dads friend that works at a beamer shop said its prob vac leaks. Im at school right now but will be going home to work on it this weekend. Any suggestions to where possibly??? All lines seemed fine to me.

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                        #12
                        Found the problem. A stem or whatever that needs a hose running to it from the throttle body was wide open since i dont have a canister hooked up so threw a cap on it and she runs like a dream.

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                          #13
                          Looks great enjoy it!

                          1986 325es (69k) Garage Queen Buy It Now 10k;1986 325es (track rat) 2.7i How-To & 1.1/1.3Motronic UpGrade
                          1991 318is (daily driver) 1991 318is M42 Maintenance How-To;1989 325i (parts car)

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