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    Mild idle roughness, ICV questions

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    Bentley manual says it should be 40 ohms but my ICV reads 30 to 40 ohms across the outer terminals, depending upon the position of the valve. Is this normal?

    Nothing seems to happen when I disconnect the ICV from its harness while the engine is running. Is this normal for cars with the three terminal ICV?

    The ICV reads 20 ohms outer to inner terminals and it flips briskly with 12v applied inner to outer.

    Given the above, should I replace the ICV?

    The backstory: I am going through my 325i m20 bit by bit, trying to track down and fix the source of a mildly rough idle. Tach barely moves from 700 rpm but I can hear her intermittently missing ever so slightly when’s she’s warmed up. It makes my Getrag 260 rattle and it’s annoying me. The car runs smoothly otherwise and just a tiny addition of throttle smooths out the idle.

    Work done to date:
    • all new vacuum lines
    • new intake boot
    • new breather hose
    • new oil cap
    • new valve cover gasket
    • valve adjustment
    • new injectors
    • new spark plugs and wires
    • new cap and rotor
    • new air filter
    • new fuel pressure regulator
    • new fuel hoses
    • new O2 sensor
    • smoke test (forgot to plug tailpipe) revealed a leaky brake booster and I have a replacement unit and grommet on the way. I plugged the line to it temporarily to see if that would help with idle, and it has not.
    Still to be done:
    • new fuel filter
    What else should I be checking? This is driving me crazy.

    Thank you
    Last edited by jgilber0; 05-25-2020, 05:27 AM.
    Jon (OO=[][]=OO)
    1992 325ic white, stock with a 5-speed swap
    Palm Beach County

    #2
    TPS, coolant temp switch, AFM, crank case vent tube seals, carbon deposit on valves (sea foam)

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      #3
      I’m starting to wonder about that crank case vent tube also. I’m sure that’s not going to be a fun job. Thanks!
      Jon (OO=[][]=OO)
      1992 325ic white, stock with a 5-speed swap
      Palm Beach County

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