Excessive fuel consumption in 2.5L Outback (MY02)

niterida · Post by **niterida** » Fri Dec 16, 2011 10:05 pm

My 2.5 Outback seems to be using a bit more fuel and have a bit of power loss recntly too.

So I cleaned my K&N airfilter - it was absoloutely and took 3 goes with the proper K&N cleaner to get it clean. I was looking through the previous owners service records and on every service for about 100,000kms it says the air filter is dirty and needs cleaned.

It also says that the radiator hoses are soft and bulged and need replacing - again for the last 100,000kms - so I replaced them too.

Stuck some fuel injector cleaner in the fuel tank.

Checked the spark plugs.

Reset the ECU to get rid of a couple of error codes.

So will have to see if any of these have any effect.

I suspect it is my cat and/or exhasut system because it is very old and the muffler is rusting away to nothing. I have a stainless WRX system (std Subaru 2.25" system) to go on but I need a proper exhaust shop to modify it to make it fit.

And if that doesn't fix my lack of power and poor fuel economy I will just have to turbo charge it

Lalbert · Post by **Lalbert** » Tue Dec 20, 2011 3:46 pm

Hello Gannon. If the knock sensor was faulty, could that explain why the fuel mix is running rich? Soon after I noticed the increase in fuel consumption, the ECU check light came on occasionally just after starting the engine. However, after a few weeks went by, the warning disappeared altogether, so I ignored it. Should I get the knock sensor replaced?

littlewhiteute · Post by **littlewhiteute** » Tue Dec 20, 2011 6:41 pm

Subaru upper engine cleaner, then 98 fuel only.

More expensive, but you will get more kms per tank, so ends up cheaper in cents per kilometre.

Venom · Post by **Venom** » Tue Dec 20, 2011 7:51 pm

Lalbert wrote:Hello Gannon. If the knock sensor was faulty, could that explain why the fuel mix is running rich? Soon after I noticed the increase in fuel consumption, the ECU check light came on occasionally just after starting the engine. However, after a few weeks went by, the warning disappeared altogether, so I ignored it. Should I get the knock sensor replaced?

The ECU activates the check engine light when something is wrong/faulty. There will be a code related to that fault which the ECU should still have stored. I'd buy a OBD/II scanner and plug it into your computer to read the ECU code, or take it somewhere to have it read because it will indicate what specifically might be causing the issue. The code numbers and their relevant faults are pretty common on the net, there will be links on the forums somewhere. Much better than guessing which $300 sensor is faulty.

Gannon · Post by **Gannon** » Wed Dec 21, 2011 5:05 am

A faulty knock sensor wont make the engine run rich, but if the ECU throws a check engine light, it will be ignoring the knock sensor and running a safe timing map, which will reduce power and increase fuel consumption

discopotato03 · Post by **discopotato03** » Wed Dec 21, 2011 10:43 am

I'd go to someone that had the relevant scan tool and get them to check for problems .
Fuel quality can change without warning particularly if say 10% ethanol suddenly appeared in it . This is not to say that Ethanol is necessarily bad its just that most things aren't really designed and tuned by the manufacturer to burn it .
Anway as was said better to check and have a fair idea which bit is out of its normal ranges than to replace expensive parts in a process of elimination .

A .

Post by **Alex** » Wed Dec 21, 2011 10:59 am

this outback isnt OBDII

you dont need any scanners/tools to read the ecu, just plug the connectors under the dash together.

taza · Post by **taza** » Wed Dec 21, 2011 12:58 pm

Alex wrote:this outback isnt OBDII

you dont need any scanners/tools to read the ecu, just plug the connectors under the dash together.

+1

Plug the green connectors together. Then count the codes. Long light mean 10 and short means 1. Don't start the car with the connectors connected, just turn the ignition on.

eg. 3x long = 30
4x short = 4
= 34

Then look up the code for Subarus that are OBD I and it should tell you what it is.

Post by **TOONGA** » Wed Dec 21, 2011 5:16 pm

If it isn't OBDII then this page has all the codes and instructions

showthread.php?t=14372

happy hunting

TOONGA

niterida · Post by **niterida** » Wed Dec 21, 2011 6:27 pm

I recall reading that they went OBDII half way through Gen 3 so it may or may not be.

Easy way to tell is to join the 2 greeen connectors together and see whether the check engine light flashes or not. If it flashes in a steady blinking then it is not OBDII and there are no error codes either current or historically, if it doesn't blink at all then it is more than likely OBDII

Post by **Alex** » Wed Dec 21, 2011 6:32 pm

my my02 liberty isnt OBDII but it is a series1

fairly sure it came out with the gen4s, but there is always a chance that gen3 series2 could infact OBDII

im watching this thread with open eyes also. Im use to my ej20 liberty getting under 8l/100km, where my 2.5l outback is up around 10.5-11l/100km.

cheers