poor fuel economy on a 97 legacy GT wagon auto

[ej20boost]

well i just bought this car.... just driving the car for 10-15 miles or so i am using up 1/4 tank :mad: and i dont have a heavy foot. there is no CEL but i notice that the coolant temp gauge takes a while to warm up to normal. i went to the subaru dealer and i ordered both coolant temp sensors(one for the gauge and other for the ECU side) i know that the ECU side tells it run a little bit richer for it warm up....
my first gas fill-up when i bought the car, i used 87... so i thought this was the problem, i put 92 but hardly saw a difference just a little bit.

i know there is problems with the knock sensors but i dont know if it applies to my situation.

you guys have any suggestions?? should i just do a basic tune up(spark plugs, airfilter, etc..)??

[)2edline]

MAY BE totally unrelated. but when i picked up my 97 BD, I was totally unaware until maybe... 2 weeks into using it that in my gas filler neck, at the bottom bend into the tank, it had corroded/rusted through, and was leaking gas all over the place.

both:
making it crazy dangerous
and
using a ridiculous amount of gas, i found that going 110 miles on a full tank wasn't really....normal.

Check underneath your car for leaks from anywhere. My car was pretty bad with rust and that had spelled disaster for my gas and brake lines.

If it is that gas filler neck problem, they are readily available at subaru dealerships.

[Huffer]

i know there is problems with the knock sensors but i dont know if it applies to my situation.

you guys have any suggestions?? should i just do a basic tune up(spark plugs, airfilter, etc..)??

Lesson 1: You should ALWAYS do a tune up on a new-to-you car unless you know the work has already been done. And the only way to be sure of that is if you have stood there watching the oil get changed etc. Run some sea foam in the gas tank, change out the PCV, get a new air filter etc.
Check for exhaust and vacuum leaks.

Lesson 2: If the knock sensor is messed up, it will retard and pull timing on the engine making it run less efficiently - in order to prevent any extreme damage. Get a new knock sensor $100.

Lesson 3: Unless you KNOW the 87 gas in your area is watered down, then don't put anything in other than 87. You're wasting money.

[Grafton]

change your thermostat, a bad one will stay stuck open allowing coolent to flow even when the motor is cold, it takes forever for the motor to warm up and kills your gas mileage.

[Reason]

Does Hawaii get shitty gas? So parts of the country gets some shit stuff. That can give you poor mpg.

[decke48]

are you having any proformance problems?
let me get this straight you only get 10-15 miles on 1/4 tank.. so you only get 40-60 miles to a tank.. if so you have a leak somewhere. either the tank has a crack. or a gas line is leaking..
if not.. a tune up is a good start, then list of other things to try if it doesnt get better, seafoam 1/3 can throw the pvc valve, and the rest in the tank, front O2, smoke check the intake/intake manifoild and exhaust manifold to the second cat, have professional done injector cleaner job(half seafoam half gasoline) or send the injectors to deatschwerks to be sonic cleaned and bench flowed. may be ecu fault change to a used ecu. after that your looking in to head/ring problems like burnd valves/seats. cracked rings...

[Okin DaVanh]

When my knock sensor sh*t the bed, I got the worst mileage ever. It was like driving a V8. As soon as I changed it : it was like going from night to day. Almost all my performance came back as well as my gas mileage.

[ShadowVlican]

do you have CEL from the knock sensor?

[sprbxr]

How many miles are you guys getting out of a tank of fuel? My 97LGT runs great but doesn't get the mileage I thought it would. This car is new to me so I really don't have anything to compare it to.

Justin

[97SLGTW]

I also had my tank draining from the filler tube. However, mine wasnt rusted, but rather where the steel tube went into the rubber bend, the hose clamp was loosened somehow. Check that area, seems to be a problem. I also drive the 97 gt wagon.

I should replace my knock sensor. Highway I get great mileage about, 400 miles on a tank, but city, its bad. maybe only half of that at best.

Good luck!

Oh, Huffer mentioned the seafoam... My car has 282,000 km on it, and I have no idea when the head gaskets were done. Its the 2.5 obviously and Im a bit concerned that running the foam might dislodge some crap and give me a head gasket leak... valid concern or unreasonable fear?

[Mikey97D]

Oh, Huffer mentioned the seafoam... My car has 282,000 km on it, and I have no idea when the head gaskets were done. Its the 2.5 obviously and Im a bit concerned that running the foam might dislodge some crap and give me a head gasket leak... valid concern or unreasonable fear?

Seafoam through the gas isn't going to make any difference to the headgaskets. I may be hesitant if you were adding it to the oil, but not the fuel.