Why does my wrx run sluggish when my gas tank is less then half?
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This is a discussion on Why does my wrx run sluggish when my gas tank is less then half? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hi Everyone I have a 2003 WRX with 52,000 miles and I notice that it drives excellent when the gastank ...

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    Why does my wrx run sluggish when my gas tank is less then half?

    Hi Everyone

    I have a 2003 WRX with 52,000 miles and I notice that it drives excellent when the gastank is completely full. But once I have less then half a tank it feels sluggish and underpowered? What can I do to fix this?

    Thanks

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    Registered User Irish_car_B0MB's Avatar
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    Quote Originally Posted by jbravo View Post
    Hi Everyone

    I have a 2003 WRX with 52,000 miles and I notice that it drives excellent when the gastank is completely full. But once I have less then half a tank it feels sluggish and underpowered? What can I do to fix this?

    Thanks
    Maybe you had a bad tank of gas in the past and havent used it all up yet. Also maybe try some fuel system treatment. Or maybe its all in your head. :lol:

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    Sammich Makin' Pwincess wrxtreme06's Avatar
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    Quote Originally Posted by jbravo View Post
    What can I do to fix this?

    Thanks
    keep your gas tank more than half full

    desiree
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    Thanks for the help guys. But I also notice that the car drives rough when its cold in the morning. Is there a way to adjust the fuel pressure? Could that be the issue?

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    Registered User teflon_jones's Avatar
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    It sounds like either your fuel filter is clogged or your pump is going (or both).
    Scott
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    I think your right teflon Jones. The car runs great with a tank full of gas. I think a tank full of gas provides high fuel pressure. Once the tank is less then half, the fuel pressure drops which might cause the car to run rough and under power. Is it a pain to change the fuel pump and fuel filter? Should I reset the ecu now that the temperatures are around the 30s?

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    Registered User wrx0131's Avatar
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    Quote Originally Posted by jbravo View Post
    I think your right teflon Jones. The car runs great with a tank full of gas. I think a tank full of gas provides high fuel pressure. Once the tank is less then half, the fuel pressure drops which might cause the car to run rough and under power. Is it a pain to change the fuel pump and fuel filter? Should I reset the ecu now that the temperatures are around the 30s?
    fuel pump is easy....just put your back seats down and its located in the trunk......i believe fuel filter is easy too.....but a way to check if your fuel pump is bad is to listen while your car is idle if your fuel pump makes any weird noises.....when my fuel filter was dirty my car ran rich and would stall at red lights......it eventually messed up my MAF sensor and my car then ran rich.....burnt my 2 of my pistons.....and yea you get the idea....so just make sure you get that checked out

  9. #8
    Registered User JUSTINSNUTSWINGER's Avatar
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    Quote Originally Posted by teflon_jones View Post
    it sounds like either your fuel filter is clogged or your pump is going (or both).
    +1
    N-swinger

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    Same problem

    My O4 is doing the same thing. Thought it was in my head at first but confirmed MPGs with half tank fill-ups vs full. Also, sluggish in the cold. Could it be water in the tank?

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    Fuel pump did it

    Thanks for the great advice. Upgraded the fuel pump to a Walbro 255 and WOW what a difference. Not only am I getting consistent fuel burn but MPG went up to 28! Car runs smoother under power and has better low RPM throttle response.

    Maybe I'll keep this Subaru after all.

  12. #11
    Registered User T.J.'s Avatar
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    Good to hear that she is running better! You should probably replace the fuel filter under the hood too, just to be safe.

    It is a snap to do and only costs $20 or so to replace. Look at the corner of the engine bay that is closest to the drivers seat. It is the small black pot w/ two curved tubes sticking out of the top. It is just held in by a metal strap and the fuel lines that are attached to it.

    Later, T.J.
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    Thanks - did it already

    Changed the filter as part of my post purchase maintenance back in February.

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