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Guest Message by DevFuse

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H4 lacks power

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6 replies to this topic

#1 bossdj



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Posted 01 September 2013 - 11:34 PM

I'm sure the answer to my problem exists somewhere on this forum, but my searches keep leading me nowhere.   So here's  the deal:  Recently purchased a 2004 outback ltd(nice car!).  The car seems to lack power when compared to the 2.2 legacy we traded up from.  The throttle response simply isn't there.  The legacy had a 5 SP and the OB has an a/t.  This is my first experience with an a/t in a suby.  Also experiencing a rough idle when in gear.  Any help or input on this would be greatly appreciated!

#2 Fairtax4me



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Posted 02 September 2013 - 01:02 AM

I'd start by checking what few vacuum hoses it has for cracks and loose fitting. A vacuum leak would cause both low power and a shaky idle.
If it has a MAF sensor (I'm not positive 04 had one) it may benefit from a cleaning with MAF sensor or electronics cleaner.
One of the big power reducers on these cars is a bad knock sensor. Generally the housing will crack and allow the sensor element to corrode and cause false readings. They seem to be about 50/50 on setting a CEL code. I have a thread about inspection and replacement of the knock sensor. It actually popped up again just a few days ago. Called knock sensor 101.

But speaking of codes, run it by autozone or similar and have it scanned for codes. Even if the Check Engine Llight is not on there may be stored codes or a pending code that could offer some clues.

#3 NorthWet


    Eeyore Incarnate

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Posted 02 September 2013 - 10:17 AM

"Lacking power" could also mean not accelerating well, which could be transmission-related.  Does the transmission seem to shift properly?  If it is in "limp mode", it would stay in 3rd gear (at least the older models do).

#4 idosubaru


    Elite Master of the Subaru

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Posted 03 September 2013 - 05:20 AM

any check engine lights?


the rough idle certainly needs taken care of.

#5 nipper


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Posted 03 September 2013 - 11:18 AM

If you are doing your own work, go out and buy a cheap vacume gauge. Throw it on the car and it can tell a lot of what is going on. Codes sometimes get you only so far.

#6 WoodsWagon


    Formerly 91Loyale

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Posted 03 September 2013 - 02:42 PM

04 should be a speed density car so no maf. Only the cal-spec pzev cars had a maf in 04, but they were only sold in the northeast or california.

#7 bossdj



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Posted 03 September 2013 - 07:13 PM

any check engine lights?


the rough idle certainly needs taken care of.

no cel.  only idles rough while in gear and at a stop/on the brake

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