Where could my vacuum leak be?
07-09-2003, 01:12 AM
#3
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Location: Ann Arbor MI
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Do you think you have a leak because of low vacuum or because you hear it hissing or because of a high idle? Check all hoses and if it is a high idle try a sport bottle full of water and squirt it around the intake mating surfaces(or anywhere else you suspect the leak is) while the engine is running and the IAC disconnected. When the water hits the leak, the rpms will drop for a moment because it is harder to suck the water in. This is how a found a leak on my Blazer. Hope this helps
07-09-2003, 01:17 AM
#5
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We are still trying to find out what it is. The vacuum on the tunercat showed it was way high at idle. But when given some throttle it dropped. Its gonna take some time to see what it is.
07-09-2003, 01:57 AM
#6
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If I'm not mistaken, you should have high vacume at idle.
If you give it the throttle, your vacume should drop to nothing.
Then if you snap the throttle back shut, you should get the highest reading on vacume that you can get.
If you're sure it is a vacume leak, take a can of WD40 or carb cleaner and spray around the intake or anywhere else that you think you're pulling air. When the car idles up, that's where you have an intake leak because the engine breathes in the spray with the air and burns it, which makes the car's RPM increase.
D Moss
If you give it the throttle, your vacume should drop to nothing.
Then if you snap the throttle back shut, you should get the highest reading on vacume that you can get.
If you're sure it is a vacume leak, take a can of WD40 or carb cleaner and spray around the intake or anywhere else that you think you're pulling air. When the car idles up, that's where you have an intake leak because the engine breathes in the spray with the air and burns it, which makes the car's RPM increase.
D Moss
07-09-2003, 09:28 AM
#7
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Originally posted by dmoss69
If I'm not mistaken, you should have high vacume at idle.
If you give it the throttle, your vacume should drop to nothing.
Then if you snap the throttle back shut, you should get the highest reading on vacume that you can get.
If you're sure it is a vacume leak, take a can of WD40 or carb cleaner and spray around the intake or anywhere else that you think you're pulling air. When the car idles up, that's where you have an intake leak because the engine breathes in the spray with the air and burns it, which makes the car's RPM increase.
D Moss
If I'm not mistaken, you should have high vacume at idle.
If you give it the throttle, your vacume should drop to nothing.
Then if you snap the throttle back shut, you should get the highest reading on vacume that you can get.
If you're sure it is a vacume leak, take a can of WD40 or carb cleaner and spray around the intake or anywhere else that you think you're pulling air. When the car idles up, that's where you have an intake leak because the engine breathes in the spray with the air and burns it, which makes the car's RPM increase.
D Moss
07-09-2003, 09:36 AM
#8
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Vacuum should be higher at more closed throttle positions (relative to rpms). Any time you suddenly open the throttle, the vacuum is going to drop. How are you seeing vacuum with Tunercat? 
Isn't it just a programmer, not a scanner?
Isn't it just a programmer, not a scanner?
07-09-2003, 10:34 AM
#9
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Originally posted by shoebox
Vacuum should be higher at more closed throttle positions (relative to rpms). Any time you suddenly open the throttle, the vacuum is going to drop. How are you seeing vacuum with Tunercat? Isn't it just a programmer, not a scanner?
Vacuum should be higher at more closed throttle positions (relative to rpms). Any time you suddenly open the throttle, the vacuum is going to drop. How are you seeing vacuum with Tunercat?
Isn't it just a programmer, not a scanner?
07-09-2003, 11:39 AM
#10
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Location: Seacoast, N.H.
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Originally posted by dmoss69
If you're sure it is a vacume leak, take a can of WD40 or carb cleaner and spray around the intake or anywhere else that you think you're pulling air. When the car idles up, that's where you have an intake leak because the engine breathes in the spray with the air and burns it, which makes the car's RPM increase.
D Moss
If you're sure it is a vacume leak, take a can of WD40 or carb cleaner and spray around the intake or anywhere else that you think you're pulling air. When the car idles up, that's where you have an intake leak because the engine breathes in the spray with the air and burns it, which makes the car's RPM increase.
D Moss
) and just go around the motor with it and when the idle races you've found the leak. This method also does not make a mess 
Marc
07-09-2003, 11:59 AM
#11
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If I watch my MAP and BAR readings from my autotap logs, the MAP approaches the BAR reading as I give the car more throttle input. My understanding is that the difference between MAP and BAR is the amount of actual vacuum in the intake.
Basically, the manifold vacuum gets closer to 0 the more I feed it throttle. So at idle is it high and as I give it gas, the vacuum decreases.
Just yesterday the exhaust shop I had install a muffler on my wife's Camaro made the mistake of spraying WD-40 on a hot exhaust pipe on an S-10 pickup they were working on. Poof! Up in flames it went. Burned the under hood insulation and stuff...
I wouldn't recommend WD-40 unless the engine is cool, or you are EXTREMELY careful with it.
You might want to try the propane trick.
Basically, the manifold vacuum gets closer to 0 the more I feed it throttle. So at idle is it high and as I give it gas, the vacuum decreases.
Just yesterday the exhaust shop I had install a muffler on my wife's Camaro made the mistake of spraying WD-40 on a hot exhaust pipe on an S-10 pickup they were working on. Poof! Up in flames it went. Burned the under hood insulation and stuff...
I wouldn't recommend WD-40 unless the engine is cool, or you are EXTREMELY careful with it.
You might want to try the propane trick.
07-09-2003, 12:34 PM
#13
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My MAP readings are around 11.5 in. Hg at idle.. Say around 600 RPM with 0 throttle input...
My MAP readings get as high as 28.6 - 29 in. Hg at WOT.
The BAR readings are usually around 29.3 or so around here.
EDIT: I believe my MAP sensor is fine, but I could be wrong. I've had SEVERAL people look at my autotap logs helping with some KR and no one ever mentioned anything about my MAP readings.
My MAP readings get as high as 28.6 - 29 in. Hg at WOT.
The BAR readings are usually around 29.3 or so around here.
EDIT: I believe my MAP sensor is fine, but I could be wrong. I've had SEVERAL people look at my autotap logs helping with some KR and no one ever mentioned anything about my MAP readings.
07-09-2003, 01:49 PM
#14
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I really dont understand what all the map and everything else means but I do know that at idle the maps were reading anywhere between 60-80 (jumping back and forth) and when I applied the throttle it dropped down to 40-50!
07-09-2003, 01:59 PM
#15
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You're probably reading in kPa (kiloPaschals) and I'm reading in "Hg (inches of Mercury), so you're seeing a Metric and I'm seeing a "standard" or English.
Read this article for info on MAP and BAR... It should help you understand more.
http://www.members.aol.com/InjuneerZZ/ScanMast.htm
This article was writting by Injuneer on this board.
Read this article for info on MAP and BAR... It should help you understand more.
http://www.members.aol.com/InjuneerZZ/ScanMast.htm
This article was writting by Injuneer on this board.