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Thread: IACV sounds like a vacuum

  1. #1
    Join Date
    Feb 2013
    Location
    San Antonio, TX
    Posts
    78
    Boat
    2002 2100v Limited

    IACV sounds like a vacuum

    350 MPI in 2002 21V. I had a backfire through the throttle body which actually popped a hose loose from the idle control valve housing. After replacing the hose Ive been hearing a very loud sucking sound in the throttle body and it was idling high at times.

    I replaced the IACV with an Duralast part and I’m still getting the sucking sound but the idle is back down to normal. If I pinch IACV line line at the throttle body the sound goes away but the motor starts to die.

    Any ideas?
    Last edited by SATige; 09-01-2019 at 11:20 PM.

  2. #2
    Join Date
    Aug 2010
    Location
    Long Beach, CA
    Age
    44
    Posts
    1,137
    Boat
    2015 Z3, 1999 2100i
    The sound is normal you just don't normally hear it. Theres supposed to be a small felt pad in there called a silencer. When you removed the flame arrestor, theres a small pocket on the outside inner diameter of the throttle body. That pocket houses the felt square silencer. You can make one of your own because they don't sell them separately.
    Fixing everyone elses boat just so I can use mine...

  3. #3
    Join Date
    Apr 2007
    Location
    Fort Worth, TX
    Posts
    1,150
    Boat
    2000 Tige 21V
    I think the Quicksilver part number is 35-863829. Available on ebay.

  4. #4
    Join Date
    Feb 2013
    Location
    San Antonio, TX
    Posts
    78
    Boat
    2002 2100v Limited
    Thanks for the responses guys. That muffler is missing from the throttle body.
    The sucking sound is definitely louder now (after the backfire), and still just as loud after replacing the control valve. I’ve never experienced a backfire like that, (carb fart) through the throttle body.

    Before replacing the control valve the idle was so high I had a hard time getting into/out of gear.

    I haven’t driven it since replacing the IAC because the sucking sound was so loud, I just assumed there was something wrong.

    What do y’all think, get the muffler, dive it and see what happens?

  5. #5
    Join Date
    Feb 2013
    Location
    San Antonio, TX
    Posts
    78
    Boat
    2002 2100v Limited
    Do y’all think the throttle position sensor could be contributing? Maybe it’s not sending a signal to the computer that would close the IACV?

    And another question (sorry), does the idle control valve “feed” air directly into the intake manifold? Is it drawing (sucking) air through the throttle body and feeding to the manifold?

    Thanks for any help on this!

  6. #6
    Join Date
    Aug 2010
    Location
    Long Beach, CA
    Age
    44
    Posts
    1,137
    Boat
    2015 Z3, 1999 2100i
    The IAC routes the air separately on that throttle body so the throttle plate should be completely closed at idle. Is it idling correctly now, just lots of sucking sound? If so, drive it. If it's still idling high, check the throttle linkage and that the throttle plate is completely closed when the throttle is at idle.
    Fixing everyone elses boat just so I can use mine...

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