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2002 legacy l with 227k, 2005 honda pilot ex-l
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Discussion Starter #1
hey all,
ive been trying to keep track of the fuel mileage on my 1999 legacy outback, 2.5L auto, but the numbers dont make sense. 3 weeks ago i had gotten around 90 miles on the first 1/4 tank, 2 weeks ago i got 137, and this week im down to 3/4 and im only at 40 miles! i expected something better, since i recently did a tune up and removed my cargo basket and spare tire from the roof (thats why the number went from the average of 90ish up to 137..), but its going down instead. my driving habits havent changed, nor has my route i drive. im really confused! the car is also having issues with being able to fill the tank, due to the filler shutting off at around 1/3 of a gallon unless i barely hold the lever to pump the gas really slowly. any ideas?
 

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03 H6 OBW & 06 WRX Sportwagon
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you may have a purge valve/tank vent or some other evap system problem. You also may have 1 or 2 additional issues. If you wanna try something quick and easy, put a can of SeaFoam in the tank with a fillup and run it for at least a coupla hundred miles.

is the check engine light on? even if not, have the system scanned and post any stored codes. some codes are 'pending' and may not set the CEL.

what's mileage on the car and it's general condition?
 

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2002 legacy l with 227k, 2005 honda pilot ex-l
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Discussion Starter #4
I've already done seafoam (the week before I got 137..), and the only cel is from the rear o2 sensor needing replacing. it came on after I did the seafoam treatment.
car has approx. 185k on it, although headgaskets, timing belt and all related gaskets were replaced 25k ago. recent tune up included plugs and wires (oem subaru), fuel filter, air filter and front o2 sensor.
 

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Gauge is stepped and simply serves as a rough estimation of your fuel situation.

Fill up all the way - zero out the ODO then fill up all the way again and do the math.

Average Mileage can't be worried about unless your WAY CRAZY low for several fueling cycles and given driving conditions. If Pilots used fuel gauges there would be planes falling out of the skies every day all day long.
 

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2002 legacy l with 227k, 2005 honda pilot ex-l
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Discussion Starter #6
I usually wait until 1/2 full then fill it, because of the fueling problem, a fully empty tank would take me 20 minutes to fill...
would 15mpg be considered crazy low for an outback? that's what I've been averaging over the last few months...I used to get that in my v8 powered truck!
 

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I usually wait until 1/2 full then fill it, because of the fueling problem, a fully empty tank would take me 20 minutes to fill...
would 15mpg be considered crazy low for an outback? that's what I've been averaging over the last few months...I used to get that in my v8 powered truck!
Obviously your car has issues starting with the Tank Vent.

Anything from faulty sensors - to plugged up exhaust system, non NGK spark plugs etc can cause poor mileage. Start going down the list
 

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2002 legacy l with 227k, 2005 honda pilot ex-l
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Discussion Starter #8
I figured there was a
problem with the vent system, just not sure where to start with the diagnoses for it.
the spark plugs and wires are factory subaru, both ngk, and the exhaust shouldn't have any restrictions since the car has no cats, and a straight pipe for a muffler..ghetto I know, but I'm saving up now to replace the exhaust..
 

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best way is to fill it up,zero the trip odo and then fill it at the SAME station. Divide miles by gallons and then keep track.

I get a good 21-22 mixed
 

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2002 legacy l with 227k, 2005 honda pilot ex-l
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Discussion Starter #10
until I get the problem with the fuel filling problem fixed, I can't get a proper gauge on how full the tank is..
 

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03 H6 OBW & 06 WRX Sportwagon
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the gauge gets a combination of readings from the sender on the pump side, and a second sender on the driver's side. There are access panels under the rear seat. perhaps there's a chafed cable from one of the sending units.
 

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2002 legacy l with 227k, 2005 honda pilot ex-l
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Discussion Starter #12
i just filled up yesterday, 9.8 gallons for 141 miles...piss poor mileage again. screw it, im going to put the roof basket and spare tire back up top..apparently they make no difference whatsoever..ill just get used to filling up alot.
i have been contemplating slamming it on some lighter wheels/tires this spring...maybe that will help..
 

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you may have a bad sensor such as an Engine Temp Sensor keeping the car in 'choke' condition or a bad knock sensor etc.

perhaps someone can suggest a shop near your city that could help diagnose the problems with your car.
 

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Subaru gas gauges aren't very linear. Each quarter will get you a different number of miles.

Even without that, 141 miles from 9.8 gallons is bad. Your car isn't running right.
 

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2002 legacy l with 227k, 2005 honda pilot ex-l
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Discussion Starter #15
I'm looking now at replacing the exhaust with a stock one, and I'm also looking at replacing the cats as well, as I've got a feeling that having them gutted isn't helping. hopefully this weekend I'll be going over things looking for problems..
 

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I wouldn't spend a dime altering a free-flowing exhaust system until i got the engine running right.

of course, all bets are off if you have altered the front O2 sensors along with the exhaust. But I doubt anything after the O2 sensors (short of a clog) is part of the problem.
 

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I just recently started noticing it, but i think something similar to this is happening to me. I dont really know enough yet to ask questions. Just stating.
 

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Yesterday I filled up until it popped and it only read 9/10 full. Then I drove 10 miles and parked it at pretty much 9/10 still. Then I started it this afternoon after a day in Florida heat and it reads 3/4. I have been noticing poor fuel economy for a while, but never like this. Could there be evaporation? Where are possible evaportation points other than the fuel cap?
 
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