12-26-2013, 03:04 PM
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#1
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,614
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Quote:
Originally Posted by san rensho
Another code I am getting is a failed evap valve. Will a bad evap valve cause a vacuum leak?
This is driving me crazy.
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Most definitely..................
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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12-26-2013, 03:28 PM
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#2
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Registered User
Join Date: May 2011
Location: Miami florida
Posts: 1,591
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Quote:
Originally Posted by JFP in PA
Most definitely..................
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Can I check if its the evap valve by pinching off the vacuum hose to the motor and seeing if the MAF values go up?
__________________
Current car
2000 Boxster 2.7l red/black
Previous cars
1973 Opel Manta
1969(?) Fiat 850 Convertible
1979 Lancia Beta Coupe
1981 Alfa Romeo GTV 6
1985 Alfa Romeo Graduate
1985 Porsche 944
1989 Porsche 944
1981 Triumph TR7
1989 (?) Alfa Romeo Milano
1993 Saab 9000
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12-26-2013, 05:18 PM
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#3
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,614
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Quote:
Originally Posted by san rensho
Can I check if its the evap valve by pinching off the vacuum hose to the motor and seeing if the MAF values go up?
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Not always as it would depend upon exactly where the leak(s) is(are). Sometimes you simply have to break down and check it with a smoke machine.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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12-26-2013, 03:35 PM
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#4
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Registered User
Join Date: May 2011
Location: Miami florida
Posts: 1,591
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Quote:
Originally Posted by JFP in PA
Most definitely..................
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Oh, and will a failing AOS also cause a vacuum leak?
__________________
Current car
2000 Boxster 2.7l red/black
Previous cars
1973 Opel Manta
1969(?) Fiat 850 Convertible
1979 Lancia Beta Coupe
1981 Alfa Romeo GTV 6
1985 Alfa Romeo Graduate
1985 Porsche 944
1989 Porsche 944
1981 Triumph TR7
1989 (?) Alfa Romeo Milano
1993 Saab 9000
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12-26-2013, 05:15 PM
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#5
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,614
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Quote:
Originally Posted by san rensho
Oh, and will a failing AOS also cause a vacuum leak?
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A failing AOS diverts vacuum to where it should not be; try pulling the oil fill cap while at an idle, if it comes off very hard (or not at all) the AOS is toast. We made a test fixture from a brand new oil cap and a vacuum gage that reads 0-20 inches of water; a good AOS should read about 5 inches of water, any higher than that and it needs to be replaced.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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12-26-2013, 05:20 PM
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#6
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Registered User
Join Date: May 2011
Location: Miami florida
Posts: 1,591
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Quote:
Originally Posted by JFP in PA
A failing AOS diverts vacuum to where it should not be; try pulling the oil fill cap while at an idle, if it comes off very hard (or not at all) the AOS is toast. We made a test fixture from a brand new oil cap and a vacuum gage that reads 0-20 inches of water; a good AOS should read about 5 inches of water, any higher than that and it needs to be replaced.
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Oil fill cap comes off easily and the vacuum is very mild, i can hardly feel it when i put my hand over then oil filler tube but I have been getting more smoke at start up lately. Today it was a pretty thick, whitish blue smoke.
So a failing AOS will create a vacuum leak?
__________________
Current car
2000 Boxster 2.7l red/black
Previous cars
1973 Opel Manta
1969(?) Fiat 850 Convertible
1979 Lancia Beta Coupe
1981 Alfa Romeo GTV 6
1985 Alfa Romeo Graduate
1985 Porsche 944
1989 Porsche 944
1981 Triumph TR7
1989 (?) Alfa Romeo Milano
1993 Saab 9000
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12-26-2013, 06:52 PM
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#7
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Track rat
Join Date: Nov 2006
Location: Southern ID
Posts: 3,701
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Check your gas cap. A bad gas cap o-ring can cause evap codes and possible a lean condition.
__________________
2009 Cayman 2.9L PDK (with a few tweaks)
PCA-GPX Chief Driving Instructor-Ret.
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12-26-2013, 06:52 PM
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#8
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Registered User
Join Date: Feb 2005
Location: It's a kind of magic.....
Posts: 6,614
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Quote:
Originally Posted by san rensho
Oil fill cap comes off easily and the vacuum is very mild, i can hardly feel it when i put my hand over then oil filler tube but I have been getting more smoke at start up lately. Today it was a pretty thick, whitish blue smoke.
So a failing AOS will create a vacuum leak?
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Yes in a way, a working AOS has a low vacuum signal (~5 inches of water) in the engine case, a blown AOS can sometimes be as high as 25 inches of water, which is why it pulls oil into the intake system, which can operate at 25 inches of mercury.
__________________
“Anything really new is invented only in one’s youth. Later, one becomes more experienced, more famous – and more stupid.” - Albert Einstein
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