Just trace the vac lines back from the intake manifold and you'll be sure to find the problem 
vacuum leak pool
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Senior User
Joined: Jun 2003
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From: Virginia
vacuum leak pool
hey, i finally decided that i do in fact have a vacuum leak. I am running about 16psi when idling after she warms up. So, i think I will try to troubleshoot and find the leak sometime soon. I wanted to see if anyone wanted to guess where the leak is. Before you guess, I don't have the old metal vacuum reservoir anymore, someone replaced it with a nice plastic one. So, just remember that if you were going to guess a rusted out canister.
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Joined: Jun 2003
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From: Virginia
so far neither carb cleaner nor starter fluid has shown any obvious leaks. I haven't tried the unlit propane torch yet, but maybe if I can't find it through other means.
I am planning on following Old_paint's method in this post https://www.ford-trucks.com/forums/6...=intake+vacuum of just shutting off all nonessential vacuum connections and monitoring the vacuum level. I think this way will be easiest, or at least more reliable.
So, I am sure I will find the leak, but I am jsut trying to see if anyone has a guess of what I will find. There are bragging rights offered up for the winner.
I am planning on following Old_paint's method in this post https://www.ford-trucks.com/forums/6...=intake+vacuum of just shutting off all nonessential vacuum connections and monitoring the vacuum level. I think this way will be easiest, or at least more reliable.
So, I am sure I will find the leak, but I am jsut trying to see if anyone has a guess of what I will find. There are bragging rights offered up for the winner.
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Joined: Jan 2006
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From: The dark carnival
You need something like this.....
Propane and starter fluid methods are a joke...not to mention you can cause other problems.
On top of that with speed density the incoming air from the vacuum leak is matched with fuel via an increase in the injector pulse width. Low vacuum DOES NOT mean a vacuum leak with SD....MAF or carb on the other hand yes that would make more sense becuase at that point you have a lean condition and that can result in a vacuum loss. Vacuum leaks with SD = high idle due to the MAP sensor.
Propane and starter fluid methods are a joke...not to mention you can cause other problems.
On top of that with speed density the incoming air from the vacuum leak is matched with fuel via an increase in the injector pulse width. Low vacuum DOES NOT mean a vacuum leak with SD....MAF or carb on the other hand yes that would make more sense becuase at that point you have a lean condition and that can result in a vacuum loss. Vacuum leaks with SD = high idle due to the MAP sensor.
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Senior User
Joined: Jun 2003
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From: Virginia
so, eco, maybe I don't even have a leak? So, how do I bring my vacuum back to where it should be? I am running at 16 inches right now while idling in park. My tranny is pissed at me right now (I think because the vacuum is telling it to shift late). The truck smells a little off... lots of little things point to an unhappy vacuum. Got any recommendations as to what I should be looking at? I can't afford the smoke machine (I cna barely afford the internet connection to look at a picture of your smoke machine).
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Elder User
Joined: Oct 2006
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From: Redmond, WA
Originally Posted by eco
Propane and starter fluid methods are a joke...not to mention you can cause other problems.
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Post Fiend
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From: Bonita Springs FL
Originally Posted by eco
Low vacuum DOES NOT mean a vacuum leak with SD
....MAF or carb on the other hand yes that would make more sense becuase at that point you have a lean condition and that can result in a vacuum loss.
Vacuum leaks with SD = high idle due to the MAP sensor.
Are you saying that a vacuum leak in a speed density motor will cause a high idle because of the map sensor (which is true) which will lead to a lower vacuum? Because doesn't that just show that a low vacuum is because of a vacuum leak?
Or are you saying that bad MAP sensors cause a low vacuum?
Post Fiend
Joined: Mar 2002
Posts: 19,402
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From: Bonita Springs FL
Originally Posted by Skandocious
If I had a nickel for every time you guys said vacuum in this thread.... 
vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum vacuum
There's a buck and a quarter. Now go pay someone to install and remove those headers every two years.
Elder User
Joined: Oct 2006
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From: Redmond, WA
Originally Posted by andym
There's a buck and a quarter. Now go pay someone to install and remove those headers every two years.
Postmaster
Joined: Oct 2006
Posts: 4,816
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From: Davis & Newcastle, CA
Originally Posted by andym
Don't forget the duct tape. I keep 6 rolls of it in the garage.
I've seen Andy's garage, he keeps spares of every fluid, tool, part, filter, you name it... Nerd.
(I'm jealous
)