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2009 Forester
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Discussion Starter #1
I recently had the 30,000 mile maintenance work done on my 09 Forester. This was on January 20th. Before having this work done I was averaging anywhere from 27 to 30 mpg driving to and from work. (I work 2 hours from where I live and drive back country 55mph highways) After the maintenance work I am now only getting 22 to 25 mpg. I have since had it back into the dealership twice for that problem and they have told me there is nothing wrong with my car. The 2nd time I was up there they hooked it up to the scanner and they reset the emissions values (I think is what they said they did) with no change. I called 2 other dealerships who have said that they have no idea what could be causing the problem and the place I bought it from can't figure it out either. I bought the car 1. because of the drive and I needed something better for winter and 2. because I heard nothing but great things about the MPG. Has anyone else with an 09 Forester had this same problem? Or even any other model. If so what was done or what was wrong with it? Any help would be greatly appreciated. I have to take it back in next Tuesday for them to once again look at it. And I'm hoping that maybe I'll find an answer for them to fix. :)
 

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2009 Forester
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13 Posts
Discussion Starter #2
I forgot to mention that it is an Automatic Transmission. And has no other problems that I know of. The check engine light has yet to come on and while hooked up to the scanner no codes appeared.
 

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2009 Forester
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Discussion Starter #4
That's what I originally thought but it was way colder before I did the maintenance work. One thing I did notice driving it the other day was that the Average MPG thing on the dash board kept bouncing up and down (24.6 to 24.9). This was while cruising at 55 mph and not braking or accelerating.
 

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09 Forester XT
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52 Posts
I had the 30K check performed on one of my two '09 XT's. Noticed the same thing, i.e. slight drop in mpg. This car is my wife's and she enjoys the turbo and "drives" the car if you will. She is fully aware of the what she can expect in terms of performance including MPG. Our fix was simple, we had the dealer reset the computer (can be accomplished by disconnecting the battery and waiting for a slight period of time before reconnecting). It was their suggestion as the dealer tech are also Subie tuners. Once my wife began driving the car, her way if you will, all is back to normal. The auto learns how you drive, however, cooler weather will change the outcome of MPG slightly. See if this helps!

Remember cooler weather changes tire air pressure, keep an eye on it.
 

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2009 Forester
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Discussion Starter #9
I had the 30K check performed on one of my two '09 XT's. Noticed the same thing, i.e. slight drop in mpg. This car is my wife's and she enjoys the turbo and "drives" the car if you will. She is fully aware of the what she can expect in terms of performance including MPG. Our fix was simple, we had the dealer reset the computer (can be accomplished by disconnecting the battery and waiting for a slight period of time before reconnecting). It was their suggestion as the dealer tech are also Subie tuners. Once my wife began driving the car, her way if you will, all is back to normal. The auto learns how you drive, however, cooler weather will change the outcome of MPG slightly. See if this helps!

Remember cooler weather changes tire air pressure, keep an eye on it.
They reset the computer at the 30K appointment and they reset it again when I brought it back up there last week. It hasn't changed. I know the cooler weather will have an effect on it but why did it happen right after the maintenance work vs when it was below zero a few weeks before. That's why I'm wondering if something isn't on properly or wasn't done right. I really like and trust this dealership and that's why I bought from them but I'm starting to question them.
 

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06 Forester
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115 Posts
They reset the computer at the 30K appointment and they reset it again when I brought it back up there last week. It hasn't changed. I know the cooler weather will have an effect on it but why did it happen right after the maintenance work vs when it was below zero a few weeks before. That's why I'm wondering if something isn't on properly or wasn't done right. I really like and trust this dealership and that's why I bought from them but I'm starting to question them.
From my experience, reseting the computer usually makes the MPG worse for about 1000 of next miles as the computer goes back to the original programmed fuel maps which in many cases are not efficient. It comes back to the regular MPG once the computer re-learns your driving habbits.
 

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2009 Forester
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Discussion Starter #11
From my experience, reseting the computer usually makes the MPG worse for about 1000 of next miles as the computer goes back to the original programmed fuel maps which in many cases are not efficient. It comes back to the regular MPG once the computer re-learns your driving habbits.
So then them undoing the battery and resetting everything at the maintenance work basically messed it up until the car relearns everything. Well there's another thing on my list that they are not going to be doing again.
 

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2007 2.5X L.L. BEAN
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151 Posts
So then them undoing the battery and resetting everything at the maintenance work basically messed it up until the car relearns everything. Well there's another thing on my list that they are not going to be doing again.
I'm not a big fan of dealerships or large chain shops, but for alot of maintenance and repair issues these days the battery has to be disconnected, or worse problems can occur other than 2-3Gal. drop in Mpg.
 

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06 Forester
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I'm not a big fan of dealerships or large chain shops, but for alot of maintenance and repair issues these days the battery has to be disconnected, or worse problems can occur other than 2-3Gal. drop in Mpg.
That's interesting, please explain.
What can get messed up with battery connected if the ignition is turned off??

The reason the dealer did disconnect the battery is:
1. They probably changed spark plugs which requires battery removal in order to get to the plugs on the turbo car (on N/A you can do without taking it out but it helps to have more room)
2. They replaced air filter which requires reset of computer as there may be different amount of air getting into the engine therefore will require stock ECU fuel map ready for new inputs.
 

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06 Forester
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So then them undoing the battery and resetting everything at the maintenance work basically messed it up until the car relearns everything. Well there's another thing on my list that they are not going to be doing again.
It basically brings the ECU to the "virgin" state which is less than optimal as you need to keep in mind that stock ECU program is designed to accommodate thousands of engines that really are not identical although are the same model.
Every stock engine although same in model, displacement, etc. has a small variation in tolerances due to various material variations of part batches, ways it's been put together and other things. Basically, although the same, all engines are not identical and stock ECU needs to be designed to accommodate all of them out of the factory. The "learning" capability of the ECU is designed to optimize the engine performance once the car is being used based on the various sensor readings obtained during driving periods. Basically, the car learns how it's being driven most of the time and optimizes engine performance according to these conditions.
 

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2009 Forester
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10 Posts
Hello,

Few months ago I have received recall notice for my '09 that stated something about emissions and computer. Can it be that dealer made a software upgrade on yours?

Sincerely,
/s/ Al
 

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2009 Forester
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Discussion Starter #16
That's interesting, please explain.
What can get messed up with battery connected if the ignition is turned off??

The reason the dealer did disconnect the battery is:
1. They probably changed spark plugs which requires battery removal in order to get to the plugs on the turbo car (on N/A you can do without taking it out but it helps to have more room)
2. They replaced air filter which requires reset of computer as there may be different amount of air getting into the engine therefore will require stock ECU fuel map ready for new inputs.
They did both of those.
 

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06 Forester
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115 Posts
Yes I really like and trust this dealership and there is no problem with it that's why I bought from them even good maintenance too.
yes it's quite possible that in order to fix the problem the easiest way, they developed a new fuel map that is richer (more gas with same amount of air) therefore decreasing the MPGs.
 

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2014 CVT
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826 Posts
That's interesting, please explain.
What can get messed up with battery connected if the ignition is turned off??
just because the ignition is off does not mean there are no hot wires.......and it is first thing you should do when working on car, it stops sparks, or getting shocked in your tracks, reduces the chances of an airbag going off, stops fuses from being blown, and damage to the ECM or any other control module on the car. think of it like this, what is cheaper, un-hooking the battery or replacing the ECM because you touched a hot wire to a ECM ground??
 

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2007 2.5X L.L. BEAN
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151 Posts
just because the ignition is off does not mean there are no hot wires.......and it is first thing you should do when working on car, it stops sparks, or getting shocked in your tracks, reduces the chances of an airbag going off, stops fuses from being blown, and damage to the ECM or any other control module on the car. think of it like this, what is cheaper, un-hooking the battery or replacing the ECM because you touched a hot wire to a ECM ground??
Thanks, what he said.
 
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