Outback 2000 getting less than 12mpg

[kksquared]

Hello,

After 4 months with our preowned Outback 2000 (37K), its fuel efficiency suddenly plummeted to less than 12 mpg (we mostly do city driving). We took it to our local mechanic who suspected it was part of 2 recalls-- Oxygen Sensor and/or Engine Control Module (ECM) Reprogramming. However, we then discovered that our car had no open recalls. Next, we took it to a Subaru dealer who ran a computer check and found no problems. He only suggested that the low gas mileage may have been due to the kind of gasoline in the car and that we fill the tank and recalculate the mpg.

 

Well, now after spending $80 with our mechanic and $106 w/the Subaru dealer, our Outback is still burning way too much gas. Has anyone had similar problems? Or have any educated guesses on what is going on?

 

We're pretty puzzled to be dealing with this when the car has such low mileage (37K).

 

Thanks.

[Skip]

Two somewhat cheap changes is what I would do

 

1) 02 sensor - they get lazy

 

2) FI thermosensor - if it gets lazy it will not

set an error code but may be fooling the

ECU into thinking the engine is running cold

[OB99W]

Next, we took it to a Subaru dealer who ran a computer check and found no problems.

Lots of things can cause bad gas mileage. As Skip mentioned, "lazy" sensors are possible. Did the dealer put a 'scope on things, or just connect to the OBDII (On-Board Diagnostics connector) and read codes? If the latter, some problems can be easily missed.

[Sweet82]

How about Fuel Injector Cleaner?

 

I have a 4cyl Trooper that was down to 11 mpg a couple weeks ago.

 

Some good quality Injector cleaner gave me a lot more power and the mileage went back up.

 

Just a thought?

Glenn,

[Cougar]

It's too bad the dealer didn't look into this further but they may have been trying to be easy on your pocket book.

 

I would check the temperature sensor for the ECM first, as others mentioned. You can check that using an ohmmeter. While the engine is cold first measure the resistance of the sensor disconnected and then measure it after the engine is at normal temperature. There should be a good difference in the readings. I think the hot reading should be lower but I don't know what the specs are.

[Andyjo]

my milage has started to suck, but a CEL poped up, fuel temp sensor! d'oh! and you can't just buy the sensor.. you've gotta replace the WHOLE fuel sending unit... arg! :-\ maybe i should bash the gas tank in with rocks...

[zyewdall]

Ouch. That IS bad mileage.

 

A bad tank of gas (like the E10 that they sell here in the winter) would give you maybe 20% less mileage -- but not half the mileage you'd expect. What were you getting before?

 

Thermostat stuck open or clogged injectors would be my guess. Does the temp guage seem normal? Also, check to see if there are any fuel leaks -- maybe it's leaking out, not being used.

 

Hello,

After 4 months with our preowned Outback 2000 (37K), its fuel efficiency suddenly plummeted to less than 12 mpg (we mostly do city driving). We took it to our local mechanic who suspected it was part of 2 recalls-- Oxygen Sensor and/or Engine Control Module (ECM) Reprogramming. However, we then discovered that our car had no open recalls. Next, we took it to a Subaru dealer who ran a computer check and found no problems. He only suggested that the low gas mileage may have been due to the kind of gasoline in the car and that we fill the tank and recalculate the mpg.

 

Well, now after spending $80 with our mechanic and $106 w/the Subaru dealer, our Outback is still burning way too much gas. Has anyone had similar problems? Or have any educated guesses on what is going on?

 

We're pretty puzzled to be dealing with this when the car has such low mileage (37K).

 

Thanks.