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1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 06-22-2007, 04:33 PM   #1
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Today I was checking vacuum pressure and I checked at elbow beside EGR that leads to the black resovoir box and while engine running I had 18 - 20 psi when I shut engine off it dropped to zero right away.I assumed I have a leak and checked all connections over and changed some, I also used TB cleaner everywhere dont see a leak.I also checked elbow at the black box,any suggestions.Sometimes my idle surges abit , today not at all and I an dealing with a cam sensor code 41.
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Old 06-22-2007, 09:58 PM   #2
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Generally speaking, unless there is a check valve on that vacuum line, there should only be vacuum present when the engine is running. Since the source of vacuum is the suction of intake air caused by the downward stroke of the pistons, when the pistons are no longer stroking, they are no longer sucking in air. When the engine is not running, a vacuum gauge should show zero vacuum or atmospheric pressure.
If there is a check valve on that line, it may be faulty or it has been turned around backwards. There could also be a leak in vacuum lines inside the car that control the AC/heater vents.
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