Excess crankcase vacuum

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May 17, 2012 | 09:09 PM

samickguy15

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Joined: Feb 2004

Posts: 379

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From: Delavan, IL

Excess crankcase vacuum

Lately my Mountaineer has had a high idle situation that more or less came out of nowhere. I was adding some oil the other day while it was running and noticed that there is alot of vacuum pulling on the oil cap. When I removed the cap, the idle dropped back down to normal. It's not throwing any codes either.

Any thoughts as to what I've got going on? PCV? Bad intake gasket? Other?

May 24, 2012 | 07:54 AM

ilovemy60ford

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Joined: Apr 2004

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I can't say that I know for sure there, but the PCV valve is a good place to start. I've never seen a bad intake gasket do that, but it does sound possible...

I hope you'll let us know what you find out!

Jun 10, 2012 | 06:45 AM

Uncle Grumpy

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I thought a blocked pcv created pressure and not a vacuum.

Jun 10, 2012 | 01:00 PM

xlt4wd90

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Joined: Sep 2003

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From: SoCal

A PCV valve can fail either by sticking open or closed, and being stuck open is like making a big leak into the intake. It's a simple thing to check in this case; see if the engine idle speed changes when you pull the valve (with its vacuum line) and plug the valve with your finger.