5.7 liter Vortec Problem

Old 07-24-2009, 07:39 PM
  #1  
kod99
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Default 5.7 liter Vortec Problem

My son has a 1999 Chev Tahoe with a 5.7 Vortec ehgine. There is a slight tapping / hissing noise coming from the left bank of cylinders. The odd thing is....when it's idling and I remove the oil filler cap the engine stumbles a bit and the idle speed drops slightly. I re-install the cap and the idle picks back up and smooths out. I have never encountered this before and think it's probably related to an intake valve (either the spring, pushrod, valve or seat). Does anyone have any ideas what may be wrong? I will pull the valve cover on Sunday but thought someone on here would know. BTW, the tapping noise is very light - not a knock - just a very light hissing tap.
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Old 07-24-2009, 08:28 PM
  #2  
MEMRACING62
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POSSIBLE LOWER INTAKE PLENUM(INTAKE MANIFOLD) GASKET LEAK. THIS ENGINE IS KNOWN FOR THIS .BUT MOST OF THE TIME IT STARTS WITH COOLANT LOSS INSTEAD OF A VACUUM LEAK
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