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91' 4 Runner burping sound when drops to idle

Discussion in '2nd Gen 4Runners (1990-1995)' started by Rooster1313, Nov 24, 2021 at 1:49 PM.

  1. Nov 24, 2021 at 1:49 PM
    #1
    Rooster1313

    Rooster1313 [OP] New Member

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    Just completed timing belt, waterpump, etc replacement, have 330K miles. Replaced number of bad vacuum lines and old hoses. Runs good, but makes burping noise when it drops back to idle. Could that be a vacuum leak, or maybe air still in the coolant system? Sounds is coming from the back side of the engine, on passenger side...at least that's how it sounds.
     
  2. Nov 25, 2021 at 9:18 AM
    #2
    trlhiker

    trlhiker New Member

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    I would say you got air in the coolant system somewhere.
     
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  3. Nov 25, 2021 at 9:51 AM
    #3
    LandCruiser

    LandCruiser Rusting away

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    My 80 did this after I replaced the wp. Air bubble.
     
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  4. Nov 28, 2021 at 2:04 PM
    #4
    Rooster1313

    Rooster1313 [OP] New Member

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    Bleeding several times hasn't solved the issue and during a test drive, the vehicle is making very little power. I'm confident the timing belt replacement was done correctly with proper timing. Could replacing vacuum hoses have created a problem...maybe a failed component was getting "bypassed" due to split vacuum lines? We also put a new O2 sensor on...could that be throwing off the mixture? We ran the diagnostic and just get constant blinking. Any ideas would be much appreciated. Thx!!

    Also, adjusting the idle mix screw as very little effect.
     
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