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Discussion Starter #1
Help,

Is anyone out there familiar with the 4.6 Northstar? Mine is prone to idle surge. Someone took off the plenum and I was wondering if I might be on the right track looking for a vacuum leak there or should I look toward the crank positioning sensor? Thank you.

Rabbit
 

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94 Eldorado, and a 99 ETC
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3,887 Posts
The plenum? I've never heard that term used before... Are you talking about the intake manifold cover? That cover is the top of a large vacuum chamber, so if you were to not put it on right, you would get surgyness.
 

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White Diamond '03 DHS (with DTS floor shift)
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Krashed is right. Probably a bad seal somewhere around the cover gasket. Your definately looking for a vacuum leak.
 

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1994 Sedan Deville
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2,146 Posts
While you're under the hood you might want to check your ISC motor. It may need to have the contacts cleaned as well as the above advice.
 

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1995 ETC, 75 Deville, Cad500 powered 73 Apollo, 94 Mark VIII
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I'm just curious, on the 93-94 intake manifold, is the top piece just part of the plenum area or the runners as well?
 

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94 Eldorado, and a 99 ETC
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The runners are there to direct the flow of the air, but the they are not sealed. So I guess you can say the plenum is part of the runners as well.

Yeah I looked up the word plenum. Funny that out of all the time I've spent working on cars, I have never heard that term before.
 

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1994 Eldorado Touring Coupe, Polo Edition, '03 CTS
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22 Posts
My '94 eldo just started doing that, surgering while ideling. I WOTed out a couple of times and it was OK. This all stated after not driving on freeways for about a month. It keeps coming back as long as I'm only doing city driving. Helps when it starts to surge throw it in park and rev the rpms. I was thinking maybe dirty fuel injectors? :hmm:
 
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