Where does the map sensor get its vacuum? - Ford Mustang Forum
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post #1 of 22 (permalink) Old 03-15-2009 Thread Starter
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Where does the map sensor get its vacuum?

Ooohhhh man I'm goin nuts
I have a 1987 Fox that has been sittin for a while because of emission issue. I am sure that the map sensor is not getting vaccume. It might not be the actual problem. I hope it is but there is a hose that comes from the M.A.P sensor and goes to some kind of one way valve with two other hoses coming from it, they both disapear outside of the engine commpartment. If I can figure out why there is no vacume to the map sensor I think she'll clean right up. To make things worse the emissions chart on the shroud is freakin gone so I have NO idea where the hoses go to or what the hell is the reason there is no vacume there. I have checked all and replcaed some of the hoses I can see. You folks are guru's I sure aapreciate your input.
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post #2 of 22 (permalink) Old 03-15-2009
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it should have manifold vac. goes to intake, big G

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post #3 of 22 (permalink) Old 03-15-2009 Thread Starter
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This hose disappears into the wheel well. I know the map gets its vacume from the manifold but i dont understand how. The hoses don't go there from that valve. seems like they go on the other side of the fire wall. I have not moved any hoses from where they were when ford put them there. It has ran fine till the drive line broke a couple of years ago, then I fixed the oil leak I had from the valve cover. I have got to find out what to do. PLEASE HELP
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post #4 of 22 (permalink) Old 03-15-2009
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My 87 fox has the vacuum coming from under the bottom side of the plenum, someone had to move those vacuums at sometime or another, Mine is also totally stock.

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post #5 of 22 (permalink) Old 03-15-2009
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That is your vacuum for your heat controls, not your maf. Your maf sensor vacuum should run straight under the plenum on the driverside

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post #6 of 22 (permalink) Old 03-15-2009
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Question

Quote:
Originally Posted by kasius View Post
Ooohhhh man I'm goin nuts
I have a 1987 Fox that has been sittin for a while because of emission issue. I am sure that the map sensor is not getting vaccume. It might not be the actual problem. I hope it is but there is a hose that comes from the M.A.P sensor and goes to some kind of one way valve with two other hoses coming from it, they both disapear outside of the engine commpartment. If I can figure out why there is no vacume to the map sensor I think she'll clean right up. To make things worse the emissions chart on the shroud is freakin gone so I have NO idea where the hoses go to or what the hell is the reason there is no vacume there. I have checked all and replcaed some of the hoses I can see. You folks are guru's I sure aapreciate your input.

is there a vacuum hose that connects to the BAP/MAP i thought it just had a little plastic piece that hung on the end of there

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post #7 of 22 (permalink) Old 03-15-2009
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The vacuum line you are holding in your hand the comes from the one way valve you are talking about and goes to the port marked A / C on the vacuum multi-port next to the brake booster on the firewall. There are the 2 vacuum lines that come from the one way valve, one goes to the manifold and one goes to the heater box under your dash.

I am getting that from my 89, I don't know for sure if the 87 and 89 models are the same.

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post #8 of 22 (permalink) Old 03-15-2009 Thread Starter
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oh man thank so much guys.

The A/C port on the tree goes straight to the intake and is in new. There is one hose that goes to the MAP sensor {in my hand}From the one way valve, then the two ports point down- One goes in the fire wall, the other in the red circle on my second post I have been looking for it to exit for days, where ever it does its probly a different looking hose with my luck.

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post #9 of 22 (permalink) Old 03-16-2009
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The picture you posted with the small, plastic vacuum line in your hand (100_3997.jpg).....that DOES NOT connect to the MAP sensor.

The MAP sensor has one large port, and it's on the bottom of the sensor. The first pic you posted in your very first post (100_3996.jpg).....look at the bottom left of the sensor and you can see the large vacuum hose connected to it, right next to the electrical connector. That's the only port in the MAP sensor and that hose goes directly to the underside of the upper intake manifold.

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post #10 of 22 (permalink) Old 03-16-2009 Thread Starter
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Quote:
Originally Posted by FoxChassis View Post
The picture you posted with the small, plastic vacuum line in your hand (100_3997.jpg).....that DOES NOT connect to the MAP sensor.

The MAP sensor has one large port, and it's on the bottom of the sensor. The first pic you posted in your very first post (100_3996.jpg).....look at the bottom left of the sensor and you can see the large vacuum hose connected to it, right next to the electrical connector. That's the only port in the MAP sensor and that hose goes directly to the underside of the upper intake manifold.


Every port underneath the intake is taken. I am starting to think it might not be correctly installed though i labeled them with phone wire when I took the intake off for gaskets.

Today I created vacume to the map sensor and she cleaned up and quit smokin. Ran smooth as can be. I need to find out why there is no vaccum to the one way valve. The hose going with the brake line into the fender is suposed to supply the vaccume , not the hose to the heater controlls. I cant trace that hose. thanks again for ANY imput!!
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post #11 of 22 (permalink) Old 03-16-2009 Thread Starter
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Ol' girls an air density by the way.

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post #12 of 22 (permalink) Old 03-16-2009 Thread Starter
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Its running so rich it has fouled another set of plugs! I hav'nt even drivin it. Can any body help???

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post #13 of 22 (permalink) Old 03-16-2009 Thread Starter
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Can anybody show a pic of where exactly the hose from the MAP sensor ties in with the manifold. I think it is hooked up wrong.

A friend told me to try resetting my timming to 10 deg post? I have my trusty haynes, wish it were a chilton.

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You said it is an air density meaning it is not speed density any more? If so, the map sensor vacuum should be plugged or capped, If it does have vacuum, it will not run right, If it is still speed density, it needs the vacuum.

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If you reach under the back of the upper plenum, you will feel a vacuum tree coming out that your fuel regulator hooks to. You will have to reach under it more towards the center of the plenum to feel the other vacuum nipple coming out, it will be closer to the driverside of the car.

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