Finally found my mpg problem

Old Aug 24, 2012 | 07:47 PM
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Default Finally found my mpg problem

Ivw posted on this forum a few times about my mpg problem and I finally got around to taking it to the dealer to have them use the analyzer on it and it's a vacuum leak.. All these other places couldn't tell me cause they would only use code scanners n not analyzers so hopefully this helps my problem.. What do u think? I'm getting 11.2 mpg as I type this.. Could it be the vacuum leak causing my problem?
 
Old Aug 24, 2012 | 08:11 PM
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Yes, A vacuum leak that effect the whole intake will just cause the RPMs to go up. But a vacuum leak to just one cylinder can cause a lean condition in just one cylinder. This means more O2 is hitting the O2 sensor. The PCM will richen all the cylinders to compensate. Now the other cylinders are running too rich causing a drop in power. Now you have to press harder on the gas to get up to speed.
 
Old Aug 24, 2012 | 09:37 PM
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Where was the vacuum leak at?
 
Old Aug 25, 2012 | 01:23 AM
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Originally Posted by Camaro 69
Where was the vacuum leak at?
I haven't been told yet all I know is that there is a vacuum concern which I only interpen as a leak.. I'll find out more on monday since I didn't take it in until today thru will keep it over the weekend which I don't know y considering they work on Saturdays
 
Old Aug 27, 2012 | 03:02 AM
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What kind of vacuum concern could they be speaking of.. Heard there isn't too many vacuum areas on our cars.. I'll find out later but I'm just trying to get a heads up
 
Old Aug 27, 2012 | 06:24 AM
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Leaking intake, It is use to be pretty common for the intake to leak air and no coolant. Also it depends on the tech you had. It is pretty easy to see a lean cylinder on a scope but figuring out if it is too much air or not enough fuel can be a little tricky. Normal with an intake you just spark carb cleaner in the suspected area and watch for a change in the scope. Sometimes something like the brake booster will start to leak and effect the closest cylinder. Noramlly we will pinch off those lined just to make sure its not that.
 
Old Aug 27, 2012 | 01:53 PM
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Originally Posted by Gorn
Leaking intake, It is use to be pretty common for the intake to leak air and no coolant. Also it depends on the tech you had. It is pretty easy to see a lean cylinder on a scope but figuring out if it is too much air or not enough fuel can be a little tricky. Normal with an intake you just spark carb cleaner in the suspected area and watch for a change in the scope. Sometimes something like the brake booster will start to leak and effect the closest cylinder. Noramlly we will pinch off those lined just to make sure its not that.
If I had a vacuum leak severe enough to effect my mpg a lot wouldn't a code be thrown?
 
Old Aug 27, 2012 | 02:43 PM
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Originally Posted by Speedfreak02
If I had a vacuum leak severe enough to effect my mpg a lot wouldn't a code be thrown?
Only if the leak was so bad the computer could not compensate. Remeber all the computer sees is the O2 sensor not each cylinder. As long as the result for the 4 cylinder is good the computer is happy.
Originally Posted by Gorn
Yes, A vacuum leak that effect the whole intake will just cause the RPMs to go up. But a vacuum leak to just one cylinder can cause a lean condition in just one cylinder. This means more O2 is hitting the O2 sensor. The PCM will richen all the cylinders to compensate. Now the other cylinders are running too rich causing a drop in power. Now you have to press harder on the gas to get up to speed.
 
Old Aug 27, 2012 | 04:52 PM
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Ok I just got the car back from the dealer. It wasn't a vacuum leak it was the fuel trim. Pretty critical part for the mileage huh?
 
Old Aug 27, 2012 | 05:59 PM
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Originally Posted by Gorn
Leaking intake, It is use to be pretty common for the intake to leak air and no coolant. Also it depends on the tech you had. It is pretty easy to see a lean cylinder on a scope but figuring out if it is too much air or not enough fuel can be a little tricky. Normal with an intake you just spark carb cleaner in the suspected area and watch for a change in the scope. Sometimes something like the brake booster will start to leak and effect the closest cylinder. Noramlly we will pinch off those lined just to make sure its not that.
Well it was my upper intake manifold gasket... I wonder how many miles that will add to my mpg? I'm getting 10 right now
 

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