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2004 Legacy Outback Limited 4 Cyl Manual
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25 Posts
Discussion Starter #1
Sometimes when I pull up to a light, my 2004 Outback will idle at a very low RPM and sound like it is about to stall out. I've never actually seen it stall, but my initial gut reation is to hit the gas to get the RPMs up. Most of the time it idles fine though. Any ideas what could cause this?

Thanks
Charlie
 

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Premium Member
01 VDC, 05 R Sedan, 06 BAJA EJ257
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15,483 Posts
Try cleaning the throttle body and the air control valve. The air control valve is mounted on the throttle body and held in place by 2 screws. It has an o-ring seal so don't lose it.

If that doesn't correct it, try spark plugs.
 

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02 Outback 2.5 5sp
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543 Posts
Something else to check out is the air assist injection solenoid/related bits. P0065 is the relavent code. Will rarely set a code, but can cause these symptoms nonetheless.

James
 

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94 Posts
mine does this too, its a lot worse right after I reset the ECU/unplug the battery, and after a few days typically goes away and idle is better.

not sure what it is
 

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06 Outback 2.5i, 06 BMW 325xi wagon, 02 2.5rs, 82 CB750, Polaris XC SP 500, and a single speed bike.
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876 Posts
mine does this too, its a lot worse right after I reset the ECU/unplug the battery, and after a few days typically goes away and idle is better.

not sure what it is
In this case - because you've disconnected the battery - the ECU needs to relearn idle. On some of the automatics I've had, the proper method to relearn idle was to set the parking brake and leave the car idling in drive for five minutes.

With my 5 speed, after the engine swap the motor wouldn't hold an idle for almost a week of driving around. Not sure what the proper method to relearn idle on a manual trans is.
 

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2004 Legacy Outback Limited 4 Cyl Manual
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25 Posts
Discussion Starter #6
Thanks Everyone. I was going to try CarDocs advice first on cleaning the throttle body and the air valve.

I can clearly see that air valve on other pics of 2004 engines, but mine is a bit different looking. This may be a dumb question, but does mine have an air valve? Here's what it looks like....



 

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01 VDC, 05 R Sedan, 06 BAJA EJ257
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15,483 Posts
Yours has an electronic throttle. No IACV. Just clean the throttle body. Carbon build up around the butterfly tends to throw off the measurement sent to the ECM. Also check the PCV valve.
 

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2004 Legacy Outback Limited 4 Cyl Manual
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25 Posts
Discussion Starter #8
Thanks

Thanks. Here's what I did....

1. Took off the throttle body and cleaned a ring of crud off the butterfly and throttle body. I didn't have a new gasket handy, so I reused the old one, but there were no obvious signs of damage.

2. Pulled out the PCV and blasted it out with carb cleaner. It seemed a bit oily, but not totally gummed up.

3. Changed the plugs. The right 2 were covered in oil. I'm guessing I have a bad valve cover gasket? I didn't change the wires. I believe they are original. The car has 115k miles on it. I was just outside looking at them in the pitch black, but didn't see any arcs. Think I should replace or keep going?

I started it up and so far so good. It doesn't have the low idle problem all the time, so I'll have to drive it around a bit before I know if the problem is gone.

Thanks again for the advice. If you've got any other pointers based on what I said above, please let me know. I'll reply in a few days to the thread and let everyone know if the problem clears up.
 

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2004 Outback Wagon EJ259 - 4EAT
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121 Posts
I had the same issue on my OBW (same drive-by-wire setup as well.) Cleaning the throttle body made a world of difference, including better drive-ability at low speeds (car was always very jumpy before cleaning the throttle body.)
 

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'14 Subi OBW, '18 Subi Forester
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1,920 Posts
It's another one of those reasons that I advise people to NOT try and clear codes by removing a battery terminal. Cabled systems that used a separate IAC had the benefit of a separate, dedicated module designed to meter very small amounts of air. Electronic throttle designs took advantage of their (in theory...) more precise control and learning ability to eliminate the separate IAC, instead relying on careful modulation of that huge throttle plate to also do idle duty. And it doesn't take much crud build-up to throw off the metering and require a lot of learning to compensate.

Remove a battery cable and wipe out that learning, and you are left with a system that for a time will not know where to set the plate.
 

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2003 LL Bean Outback H6 and 2019 Outback Base
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514 Posts
Mine idles at about 400 with nothing running...once warmed up........I think its a " Subaru" thing....

new Iacv and throttle sensor, new plugs as well were done

My wifes 2006 2.5 automatic is similar also....
 
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