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2004 CTS 3.6 and 2001 Seville SLS 4.6
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5 Posts
Discussion Starter #1
2001 SLS. Removed plenum to replace boot. My question is, there is a valve with a small hole in the center on the plenum below where the boot slips on, that is held in place by 2 torx screws. What is this valve? And should you be able to blow thru the little hole?
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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26,323 Posts
It's an overpressurization valve (or backfire valve). It's there to keep the plenum (manifold) from cracking in the event of a backfire.

The valve itself should not be able to be blown through, but the hole in the plastic is not a sealed part of the valve.
 

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2004 CTS 3.6 and 2001 Seville SLS 4.6
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5 Posts
Discussion Starter #3
Thank You

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If it were bad would it cause it to not idle?
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Yes, if it where stuck open it would be a big vacuum leak. That said, I've never heard of that before. If you had an idle problem and a P0171 & P0174 code, it was caused by the ripped plenum.

P.S.
Be sure to give the TB a good cleaning while you are in there.
 
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