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Old 08-03-2012, 10:05 PM   #1
Pickler
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Member#: 301247
Join Date: Nov 2011
Location: Toronto
Vehicle:
09 Impreza 2.5i MT
White

Default suddenly poor throttle response and MPG

hello guys i have an 09 impreza 4eat with 35k miles.

my throttle is not as sharp as it used to be and there seems to be total lack of power below 3500rpm now. i used to zip in and out of traffic at 3000rpm fine but this is impossible now. sometimes i have to floor the car on passes at 40mph. pathetic. im currently getting 20mpg on my daily route which i used to always get 24mpg. also my highway mileage wont climb past 28 anymore at 65mph. it seems like its getting worst. this has been the hottest summer on record and yes my A/C use has increased but cmon 4mpg drop?? what's with my throttle being so dull now? my scanggauge reports air2fuel ratios of ~14.6 cruising and about 11.5 WOT at high rpms. i had a major tune up that cost me nearly a $1000 at the dealership. included plugs, air filter, atf, atf filter, differential, brake fluid flush, alignment, balancing, brake pads and rotors plus various inspections. im out of ideas...whats wrong with my suby?
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Old 08-05-2012, 03:53 AM   #2
MarcoPolo360
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Join Date: Nov 2010
Chapter/Region: E. Canada
Location: London, Ontario
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2011 2.5i 5MT
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The heat and the A/C usage would definitely be contributing factors to the problems you're describing, but I don't know by how much...

You could always try resetting the ECU (disconnecting the battery for 30 seconds) to see if that fixes it...

If you do reset it, don't bring the car to a dealership until you've started/stopped the engine a few times (or if you do, tell them your battery died very recently).
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Old 08-05-2012, 04:48 AM   #3
Pickler
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Join Date: Nov 2011
Location: Toronto
Vehicle:
09 Impreza 2.5i MT
White

Default

yea I did think maybe it was something with the ecu. but disconnecting thr battety did not make any difference. throttle feels the same. also I noticed that on 100% engine load bellow 2500rpm engine makes this wierd noise; engine sound just changes. I can describe it as engine droning sound, it's a bit snarly and lower pitched. this gets worst if ac is on. but if I downshift and get more torque engine then sounds normal.
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Old 08-05-2012, 07:02 AM   #4
Leviman
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Did the problems emerge after the 'tune up'? If problems weren't there and then were, and there was an event almost directly between them, chances are good, that could be the culprit.
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Old 08-05-2012, 04:28 PM   #5
Pickler
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this happened since two weeks ago. my tune up was over a month before. I did have an oil change couple weeks ago with German castrol and oem filter.

also since I bought this car I noticed this air rushing sound when applying a bit of throttle. sounds like my airbox isn't tight or something.

Last edited by Pickler; 08-05-2012 at 09:27 PM.
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Old 08-06-2012, 12:58 AM   #6
MarcoPolo360
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Join Date: Nov 2010
Chapter/Region: E. Canada
Location: London, Ontario
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2011 2.5i 5MT
World Rally Blue

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Check to see if your air filter box is closed properly.
EDIT: This box:

Last edited by MarcoPolo360; 08-06-2012 at 02:05 AM.
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Old 08-06-2012, 01:17 AM   #7
klaus_b2
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might be a bad cat? i think they cause bad gas/loss of power but im not quite sure
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Old 08-06-2012, 11:22 PM   #8
Pickler
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Join Date: Nov 2011
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09 Impreza 2.5i MT
White

Default

ok i checked the airbox. the teeth on the left side do not seat properly in the groves or place. there is a bit of gap. i really fiddled with it but i cant get it to close neatly like on the other side. i really think something is wrong with the box. is this covered under extended warranty?
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Old 08-07-2012, 04:55 AM   #9
MarcoPolo360
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Location: London, Ontario
Vehicle:
2011 2.5i 5MT
World Rally Blue

Default

Quote:
Originally Posted by Pickler View Post
ok i checked the airbox. the teeth on the left side do not seat properly in the groves or place. there is a bit of gap. i really fiddled with it but i cant get it to close neatly like on the other side. i really think something is wrong with the box. is this covered under extended warranty?
See if everything inside the box is seated correctly.
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Old 08-08-2012, 03:16 PM   #10
Pickler
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Member#: 301247
Join Date: Nov 2011
Location: Toronto
Vehicle:
09 Impreza 2.5i MT
White

Default

yep i took it to the dealership and the mechanic said everything looks ok. although i think he just wanted to get rid of me. he said as long as the top 2 clips can close its all right. anyway i have an appointment for the air rushing and light rumbling sound that i get at high engine load.
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