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Old 05-18-2008, 11:33 PM   #1
bard329
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Default gas mileage question and rough idle question...

I just picked up a 97 legacy (auto). it runs fine for the most part. no check engine light or anything... but the two problems i'm having are:

1. When i'm at a red light, warmed up or no, it idles pretty rough. Although, sometimes after a minute or so of rough idling, it'll smooth out again. This only happens when it's in drive. if i put it in neutral or park, it's a lot smoother.

2. gas mileage. the day i got it, it had a quarter of a tank left according to the gauge. i filled it up. i put 8 gallons in because it apparently already had 8 gallons in it (16 gallon tank, right?) so if it was half full, why is the gauge reading 1/4? and on top of that, i filled it up, since then i've driving 160 miles and the gauge is back down to 1/4 (i really do not have a lead foot, btw).

i have a feeling the mileage and the idle problems may be related? i'm just not sure if the ej25 has any little quirks that could cause this, i'm new to subaru's.

also, any other advice regarding maintenance and such for a legacy newbie?


btw, i did search before i posted... i honestly couldn't find much of anything in the thousands of results that came up....... so don't flame me please
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Old 05-19-2008, 12:04 AM   #2
Frogsthatmoo
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1. That's not your idle. It has to do with your transmission. I have no idea why, but I imagine someone on here does. I've found that letting the car roll forward just a hair will reduce the vibration a lot.

2. I'm confused, but our gas tanks are only 12-13 gallon tanks. I usually get about 240-260 miles to a tank.
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Old 05-19-2008, 12:40 AM   #3
bard329
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Quote:
Originally Posted by Frogsthatmoo View Post
1. That's not your idle. It has to do with your transmission. I have no idea why, but I imagine someone on here does. I've found that letting the car roll forward just a hair will reduce the vibration a lot.

2. I'm confused, but our gas tanks are only 12-13 gallon tanks. I usually get about 240-260 miles to a tank.

really? i thought i read somewhere that it was a 16 gallon tank.... so 160 miles on 3/4 of a tank is normal?

ok, so according to cars.com it's a 16 gallon tank... is that incorrect?
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Old 05-19-2008, 09:08 AM   #4
Frogsthatmoo
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I'm pretty sure it's only a 12 gallon tank, maybe 13. I've never been able to put more than 11 gallons in my tank, even when I run it to about 280 miles on a single tank.

160 miles on 3/4 of a tank is ok, but you're obviously a lead foot :P I get about 190-200 on 3/4's
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Old 05-19-2008, 09:23 AM   #5
illegal2.2
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o rly^
i think our tank has like 14.9 in it or something. i've put at most 12.5 gallons in at some point of time.

chingchong
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Old 05-19-2008, 09:50 AM   #6
SLegacy99
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Our tanks are 15.9 gallons.

I've found that both of my Legacies have innaccurate guages. Go by mileage. When I had an auto LGT I averaged 19/29.

I suggested you try calculating your mileage and see what you get.
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Old 05-19-2008, 11:52 AM   #7
RallyLegacy
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yep, my 97 L is a 15.9 gallon tank. Our gauges seem to sit toward F for quite a while and then drop really fast to E and then sit there a while, and then the light comes on. The light comes on with about 2.5 gallons left (at least in mine), so even if you wait till the light comes on you should still be fine.
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Old 05-19-2008, 01:43 PM   #8
bard329
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Quote:
Originally Posted by RallyLegacy View Post
yep, my 97 L is a 15.9 gallon tank. Our gauges seem to sit toward F for quite a while and then drop really fast to E and then sit there a while, and then the light comes on. The light comes on with about 2.5 gallons left (at least in mine), so even if you wait till the light comes on you should still be fine.

so the gauge isn't accurate, but the light is?
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Old 05-19-2008, 02:40 PM   #9
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Quote:
Originally Posted by bard329 View Post
so the gauge isn't accurate, but the light is?
The guage is variable. You go through the first half slower than the second half.


Quote:
Originally Posted by RallyLegacy View Post
yep, my 97 L is a 15.9 gallon tank. Our gauges seem to sit toward F for quite a while and then drop really fast to E and then sit there a while, and then the light comes on. The light comes on with about 2.5 gallons left (at least in mine), so even if you wait till the light comes on you should still be fine.
You just described exactly what mine does.
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Old 05-19-2008, 03:39 PM   #10
RallyLegacy
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Quote:
Originally Posted by bard329 View Post
so the gauge isn't accurate, but the light is?
As far as I can tell it is. I didn't know my car even had a light until I ran it way past where I would usually fill it up (didn't know the size of the gas tank at the time) and the light came on. I usually just run it to the light, and I still have at least 2 gallons left.
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Old 05-19-2008, 04:03 PM   #11
Frogsthatmoo
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Quote:
Originally Posted by RallyLegacy View Post
As far as I can tell it is. I didn't know my car even had a light until I ran it way past where I would usually fill it up (didn't know the size of the gas tank at the time) and the light came on. I usually just run it to the light, and I still have at least 2 gallons left.

Yeah, I didn't even know I had a gas light until a couple months ago.


Ok, I guess I was wrong. I usually only put in 11 gallons because the needle is at the E peg. I'm thinking about just running the car until it runs out to see how far I can really go.

Sorry about my misinformation.
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Old 05-19-2008, 05:05 PM   #12
bard329
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Quote:
Originally Posted by Frogsthatmoo View Post
Yeah, I didn't even know I had a gas light until a couple months ago.


Ok, I guess I was wrong. I usually only put in 11 gallons because the needle is at the E peg. I'm thinking about just running the car until it runs out to see how far I can really go.

Sorry about my misinformation.

uhm.. i've heard thats bad... if you run it till it just shuts off for lack of fuel, it kicks up all the sediment in the bottom of the tank which then clogs your fuel filter and fuel injectors
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Old 05-19-2008, 05:29 PM   #13
RallyLegacy
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Quote:
Originally Posted by bard329 View Post
uhm.. i've heard thats bad... if you run it till it just shuts off for lack of fuel, it kicks up all the sediment in the bottom of the tank which then clogs your fuel filter and fuel injectors
I heard that there is ~1gal at the bottom of the tank that is below the fuel pickups. If that is right then all the sediment or whatever is in your tank will stay there, since your fuel pickups won't be able to suck all that up.
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Old 05-19-2008, 05:29 PM   #14
Frogsthatmoo
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Quote:
Originally Posted by bard329 View Post
uhm.. i've heard thats bad... if you run it till it just shuts off for lack of fuel, it kicks up all the sediment in the bottom of the tank which then clogs your fuel filter and fuel injectors

Trust me, the way I drive, I kick up sediment all the time


And you're probably right, but I doubt it would have much of an impact on the car seeing as I would only do it once. It's not like I like to run out of gas.
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Old 05-19-2008, 07:56 PM   #15
SLegacy99
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Anybody ever have a fuel system clean out? I'm blanking on what all they did, but it was more than just your STP fuel injector cleaner.

I had my done a couple years back. My fuel economy went up afterwards.
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Old 05-19-2008, 09:06 PM   #16
97legacygt
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I also have 97 legacy, and i have never put more than about 12 gallons on it even when the needle is on E. I believe this is because most cars have a safety feature where the manufacturer has anywhere from 2-5 gallons left in the tank when the needle is on E. This is so people don't fill up before they are on E. This is for the people's convenience so they don't run out and it is better for the car and engine.
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Old 05-19-2008, 11:04 PM   #17
Jonathan
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Actually this 12 gallon fill-up on a 15.9 gallon tank isn't that unusual.

This is how lots of manufacturers have set their cars up.

The idea is that these new fangled in-tank electric fuel pumps run best when surrounded by gasoline (which helps them stay cool) and by leaving the extra three to four gallons in the tank, helps keep sludge, dirt and grime at the bottom of the fuel tank (where it belongs) instead of being pumped through the fuel filter.

Sure, you can be brave and try running through ALL your fuel before refueling, or you can be sensible and toss in the 11 or 12 gallons with your gauge reads "Empty". By only adding the 12 gallons, you are doing your fuel pump and filter a favour.
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Old 05-20-2008, 09:27 PM   #18
linsavy
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I tried a bunch of things to "fix" the idle shake when in gear. Nothing really fixed it. I tried new engine mounts, changed fluid, throttle body clean, replaced IAC, new O2 sensor, new spark plugs, new shortblock after the bearings gave out. Nothing... I figure it must be in the tranny, torque converter or TCU as they were the only things not yet replaced. It is worse when it is cold out.
Try some Chevron Techron gas it may help with the fuel gauge issue.
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Old 06-16-2008, 07:42 PM   #19
bard329
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so far i've changed out the pcv valve, air filter, spark plugs, oil, poured in some oil and gas additive (injector cleaner and whatnot).

it still shakes pretty rough when i'm in drive or reverse. neutral and park is just fine. any other suggestions? its kind of annoying so i'd really like to get this fixed.

and yes if i let the car roll forward a bit it does lessen the shaking. so is this really a trans issue? is it harmful? i'd imagine if it was damaging to the car, someone would have had to fix the aftermath of it (which in turn would give us a clue as to what the problem is).

should i just not worry about this? after the highly modified cars i've had before this (this one is stock, though) i'm used to getting very paranoid about noise and irregular behavior when it comes to any car i drive.


anyway, any other advice to take care of this car i've had for a month now? i'm getting the trans fluid flushed out next week. what should i do to make sure this car lasts as long as possible? (oh and i found out last week that the headgaskets have been replaced with the better thicker ones a while ago
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Old 06-17-2008, 12:32 AM   #20
birukun
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How many miles? I have heard that if you have high mileage and you flush your tranny, as in it has not been done in a LONG time, this could be the last days of your transmission. Something about friction material floating in the fluid.

Have you tried to save some $$ and just do the 4 quart dump once or twice? You may also consider changing the exterior filter if you have one. It is not much harder than an oil change, except that little external spinoff filter was a bear to get off. Go OEM with replacement. And make sure you have *enough* fluid after you change it. Maybe you are running low right now and don't know it. (Run through all the gears on the selector before checking, in Park, idling)

It helped smooth my idle out. Still shakes a bit, but seems much better than before.

Change the diff fluids as well. 2 liters = 1.1 up front, .8 for the rear. (on my 99, Check your user manual!)

How are those spark plug wires looking?
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Old 06-17-2008, 12:40 AM   #21
Kansei
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there is an injector cleaning machine that shuts off your fuel pump seperates the fuels system(injectors and rails) then uses a special chemical that burns like gas but completely cleans out your system. I have done a few of those now, but the fun part is when you start to run empty the engine gets jumpy and sounds like you have lumpy cams.
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Old 06-17-2008, 09:39 AM   #22
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Quote:
Originally Posted by bard329 View Post
so far i've changed out the pcv valve, air filter, spark plugs, oil, poured in some oil and gas additive (injector cleaner and whatnot).

it still shakes pretty rough when i'm in drive or reverse. neutral and park is just fine. any other suggestions? its kind of annoying so i'd really like to get this fixed.
Check your transmission/engine mounts - is the engine slopping around? Open the hood and have a friend shift it into Drive with the parking brake on and check out it. Maybe put it into Park and rev it a little and see if the engine is shaking around a lot.
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