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Weird stumble after coming to a stop ... Stock '11 2.5i Premium


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So I've just noticed this recently; whether or not it's been noticed by others, I'm not sure, but a search only came up with issues on modded cars ... which mine is not.

 

Background...

It's a 2011 2.5i Premium CVT with 37000 miles on the clock. I've been getting 32+mpg on it to work and back. Drives perfectly fine and I feel no lack of power. The only mod I have on it is 18" Rims.

 

Issue...

After driving at highway speeds for extended periods of time and I come to a stop after an exit (at the lights), I feel the engine stumble for a bit before resuming to idle at normal rpm. Now if I only momentarily stop; due to the traffic already starting to move, and I get on the gas immediately .. the car feels like it would almost stall out for a second, then picks up and goes like normal.

 

Kinda weird feeling, not sure if it's fueling/trans/etc. ... anyone experience this kinda behavior? Ofcourse it only happens after the 36K warranty expires (have extended), and it only just had its 30K service at about 35K. The only thing I'd probably check would be a vacuum leak if they messed up the inlet duct when installing a new filter ... ?

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Did the weather change much during the time you were cruising on the freeway? Change elevation much? If you're sitting in one load range for a while, it's possible ambient temperature and pressure changed enough that some rapid re-learning is required when stopping and coming down to the idle range. It takes a moment for that to happen and in the meantime you'd expect some lumpy running while fueling is adjusted.
Obligatory '[URL="http://legacygt.com/forums/showthread.php/2008-gh8-238668.html?t=238668"]build thread[/URL]' Increased capacity to 2.7 liters, still turbo, but no longer need spark plugs.
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Manuals do it is as well. If I look at the tach while its happening, the idle rpm only drops about 50rpm when its happening. I just think Subaru set the idle rpm as low as it could and still have a smooth idle. if the rpm drops a little, the engine run rough.

 

I have a manual and when engaging the clutch I also notice the engine does not like for its rpm to drop below the idle rpm.

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  • 5 weeks later...
The tech at my dealership told me this morning that this was caused by a dirty throttle body. They recommend that you have this serviced/cleaned every 60 miles or sooner if you experience any rough idling. I don't know if any of this is true or not, but I'm going to attempt to clean mine in the next couple of weeks.
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So I've just noticed this recently; whether or not it's been noticed by others, I'm not sure, but a search only came up with issues on modded cars ... which mine is not.

 

Background...

It's a 2011 2.5i Premium CVT with 37000 miles on the clock. I've been getting 32+mpg on it to work and back. Drives perfectly fine and I feel no lack of power. The only mod I have on it is 18" Rims.

 

Issue...

After driving at highway speeds for extended periods of time and I come to a stop after an exit (at the lights), I feel the engine stumble for a bit before resuming to idle at normal rpm. Now if I only momentarily stop; due to the traffic already starting to move, and I get on the gas immediately .. the car feels like it would almost stall out for a second, then picks up and goes like normal.

 

Kinda weird feeling, not sure if it's fueling/trans/etc. ... anyone experience this kinda behavior? Ofcourse it only happens after the 36K warranty expires (have extended), and it only just had its 30K service at about 35K. The only thing I'd probably check would be a vacuum leak if they messed up the inlet duct when installing a new filter ... ?

 

This is all ECU related happend to several of us 4th gens folks (I wrote a thread about it) you come to a stop and get that stumble like you about to stall it then RPMs jump back up. Highway speed or even 35-40MPH it would happend to me. YOu have a CVT but us MT guys would also have the stumble at low RPM situations like traversing parking lot/garages.

 

It took them 3 tries to fix mine, there could be a SOA technical bulletin out pertaining to the issue in which case all costs are covered. The first time they reset ECU, second time reset ECU third time the reflashed with update ROM from SOA aimed at solving the issue and that worked like a charm! It isn't related to any type of sudden re-learning by the ECU it is related to tip-in tables and torque tables used by the TB and ECU.

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This is all ECU related happend to several of us 4th gens folks (I wrote a thread about it) you come to a stop and get that stumble like you about to stall it then RPMs jump back up. Highway speed or even 35-40MPH it would happend to me. YOu have a CVT but us MT guys would also have the stumble at low RPM situations like traversing parking lot/garages.

 

It took them 3 tries to fix mine, there could be a SOA technical bulletin out pertaining to the issue in which case all costs are covered. The first time they reset ECU, second time reset ECU third time the reflashed with update ROM from SOA aimed at solving the issue and that worked like a charm! It isn't related to any type of sudden re-learning by the ECU it is related to tip-in tables and torque tables used by the TB and ECU.

 

Thanks, will check into that!

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