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Thread: low boost

  1. #1
    Join Date
    May 2006
    Location
    Moline, IL.
    Posts
    94

    Unhappy low boost

    I have a 90 anniversary and it only putting out 7 lbs of boost. sc is working fine just changed the oil in it and it spins free with no play and I can't find any air leaks in the i/c tubes what should I do first. please help.

  2. #2
    Join Date
    Oct 2004
    Location
    Howell, MI
    Posts
    971
    start the motor and spray carb cleaner/starting fluid around the intake manifolds while it is idleing, and see if the motor revs. I suppose the line from the back of the plenum through the firewall and to the boost gauge could have slipped partically off one of the fittings or it could have a cracked a little and the gauge would be showing the wrong reading.

    Was this something that came on slowly or was it all at once?
    Is the vaccuum at idle still good?

  3. #3
    Join Date
    May 2006
    Location
    Moline, IL.
    Posts
    94
    vaccuum is good at idle the line that goes in to fire wall good with no cracks and no rev with the starting fluid and it's been loseing boost over time not all at one time. you can definitely tell a lose in power.

  4. #4
    Join Date
    Oct 2006
    Location
    48125,michigan
    Posts
    4,137
    mine has the same prob some times so days my boost will b at 12-13psi and other days its 9-10psi what could cause this

  5. #5
    Join Date
    Apr 2002
    Location
    San Bernardino, CA
    Posts
    4,523
    belt slippage? also check the bypass valve if its loose or out of adjustment it will effect boost a loose vac motor at bypass can cause it to stay open and not build up boost as high as it can.

  6. #6
    Join Date
    Oct 2006
    Location
    48125,michigan
    Posts
    4,137
    how would u check this valve i know were it is located

  7. #7
    Join Date
    Apr 2002
    Location
    San Bernardino, CA
    Posts
    4,523
    make sure it closes when engine is off you can adjust it with pliers . small srew with head cut off it should open when engine is idleing and close at wide open throttle or engine off

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