Question about 1998 Chevrolet Tahoe

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1998 gmc 4x4 runs poorly and sounds like a vacume,air leak .

1998 5.7 vortec in my 4x4 sounds like i have vac/air leaking on driver side of motor and runs like it is out of time . ijust replaced spark plugs ,timing chain cover and took off injecter manifold to check for cracks .found some loose inj,manifold bolts but that was it put back together an runs better but not fixed pls help.

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The 5.0l and 5.7l all have this problem at some time.The lower intake gaskets are bad.and are sucking air which will cause the eng. to idle high and sound like like there is a cylinder or two that are not firing and you also may loose antifreeze.The upper intake is black/plastic and the lower is aluminum.Tightening the lower intake bolts may seem to help but once the gaskets are blown,they need to be replaced.If its sucking more air through the bad gasket than the TBI it will not get the right air to gas mixture.Check that all vacuum hoses are in good shape and the vacuum line that runs from the top of the upper intake to the brake booster is sealed good in the intake.Hope this gives you a better idea.

Posted on Mar 03, 2009

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I know this is going to sound way to simple, but I would look for a air leak on the intake side. The reason I say this is that your engine runs because the computer feels it knows EVERYTHING about EVERYTHING.. Kind of like *********** N law. Well, when you get a vaccum leak, the computer doesnt know its stupid and raising the idle or POOR idle is one of the effects.

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