02 subaru legacy2.5 rough idle and it dies

Both need a service
also
if carby ..running rich or choke is stuck

if EFI 02 sensors engine light should be on
idle control valve

try the crank speed/position sensor as this controls the engine revs as well as other things

The hum is likley your fuel pump priming the fuel delivery system. I would start looking at the wiring coming from the Throttle Position Sensor. With the key in the ON position, you should be getting a 12vDC (or a little higher) signal to one wire and an excellent ground on another (usually the center if there are 3). If you are missing a good ground or the 12v signal, there lies your problem. Good luck.

It can be issue with low fuel pressure,the fuel pump is getting old both needs to be checked.Also get the IAC valve checked.
Go through the related help links with similar problem,it may help:---
Click the links below:---
Engine Idles Rough and Dies? http://whatisbyme.blogspot.in/2012/05/1994-lexus-es300-engine-idles-rough-and.html

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van idles rough? http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html

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runs lean and idles rough? http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html

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Car still runs Rough after tune up?

http://howtobyme.blogspot.com/2011/12/car-still-runs-rough-after-tune-up.html

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2006 kia rio runs rough http://technoanswers.blogspot.com/2012/10/2006-kia-rio-runs-rough.html

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Idle flair is noticed on car? Rough idle? car will not idle? Erratic idle speed? http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html

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Rough idle, staling and Erratic shifting? http://technoanswers.blogspot.in/2012/03/rough-idlestaling-and-erratic-shifting.html

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These details will help.
Thanks.

Check the help links related to this problem.Click the link below to go through its troubleshooting procedure :-----Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html---------
Car won't start without hitting the gas pedal? http://schematicsdiagram.blogspot.com/2011/12/car-wont-start-without-hitting-gas.html
-------Complete loss of brake pedal then all gets normal? http://repairhelpcenter.blogspot.com/2012/01/complete-loss-of-brake-pedal-then-all.html
------Car dies when gas pedal is pressed? http://schematicsdiagram.blogspot.com/2011/12/car-dies-when-gas-pedal-is-pressed.html
--------Pushing on the gas pedal, but the car slows down? Gas pedal to the floor and the car slows down?

http://technoanswers.blogspot.in/2012/02/pushing-on-gas-pedal-but-car-slows-down.html

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After replacing brake rotors and pads, brake pedal remains on floor? http://technoanswers.blogspot.in/2012/02/after-replacing-brake-rotors-and-pads.html

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accelerator pedal sensor? http://technoanswers.blogspot.in/2012/02/2009-chevy-impala-accelerator-pedal.html

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For rough idle issues and problem troubleshooting,go through the help links provided below :----- van idles rough?

http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html

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will not idle when cold?

http://technoanswers.blogspot.in/2012/02/ford-explorer-40-will-not-idle-when.html

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runs lean and idles rough?

http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html

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Engine stumbles coming off idle when warm?

http://repairhelpcenter.blogspot.com/2012/01/engine-stumbles-coming-off-idle-when.html

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Erratic idle on car?

http://schematicsdiagram.blogspot.com/2011/12/erratic-idle-on-car.html

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Low idle when cold out side?

http://repairhelpcenter.blogspot.com/2011/12/low-idle-when-cold-out-side.html

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Idle Air Control (IAC) Valve Replacing?

http://schematicsdiagram.blogspot.com/2011/12/gmc-idle-air-control-iac-valve.html

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Engine quits at idle?

http://repairhelpcenter.blogspot.com/2011/10/engine-quits-at-idle.html

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Car overheats and Air blows hot at idle?

http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html

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While stop engine idles like cylinder missing?

http://schematicsdiagram.blogspot.com/2012/01/while-stop-engine-idles-like-cylinder.html

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This will help.

Thanks.

For this types of problem,there are few help inks to troubleshoot the problem.Click the link below to go through the troubleshooting procedure to resolve the issues :----Idles rough and quits when gas pedal is pressed less? http://technoanswers.blogspot.in/2012/01/1999-ford-f-150-idles-rough-and-quits.html-----------van idles rough? http://howtobyme.blogspot.in/2012/01/2004-ford-freestar-van-idles-rough.html
--------------runs lean and idles rough? http://technoanswers.blogspot.in/2012/02/ford-runs-lean-and-idles-rough.html
-----------Car still runs Rough after tune up? http://howtobyme.blogspot.com/2011/12/car-still-runs-rough-after-tune-up.html
------------Idle flair is noticed on car? Rough idle? car will not idle? Erratic idle speed? http://technoanswers.blogspot.in/2012/02/idle-flair-is-noticed-on-car-rough-idle.html
----------High rpm in neutral? Inconsistant high RPM in neutral? http://technoanswers.blogspot.in/2012/02/high-rpm-in-neutral-inconsistant-high.html
------------Engine Backfires? http://technoanswers.blogspot.in/2012/02/jeep-backfires.html----------- Nissan stalls and bucks on Acceleration?

http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-stalls-and-bucks-on.html

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Nissan Pathfinder Backfires? http://technoanswers.blogspot.in/2012/02/nissan-pathfinder-backfires.html
---------How to adjust rpm? http://schematicsdiagram.blogspot.com/2011/12/how-to-adjust-rpm-on-2009-dodge-charger.html
------------Engine cuts out at 3000 RPM? http://schematicsdiagram.blogspot.com/2011/12/engine-cuts-out-at-3000-rpm.html
----------This will help.Thanks.

run the fault codes
indicates an injector problem
dirty injectors, low fuel pressure , wiring are all possible issues

u should definitely get ur engines computer system scanned to avoid misdiagnosing ur isssue. once u retrieve ur eng codes u can then begin to decide which one of ur 25 sensors are acting up, or where to start lookin an testing for ur fault..... good luck

replace the 02 sensor or the egr valve in the intake manifold needs replace or cleanout and is carboned up

Could be the Idle Control Valve?