Apart from the obvious loud pedal excess, is there anything that can suddenly cause a car to become excessively thirsty.

I have a UK MY00 Turbo
62,000 miles
Full Decat
Itg
DAWES
AE801 ECU

Normally, I brim the car with optimax + Booster and tended to get 60 miles per qtr tank (I could work out mpg but you know what i mean )

Maximum i'd get is about 240 - 260 miles per tank, and that's the way it's been for 3 years.
Suddenly I'm getting 200 miles per tank and i ain't doing anything different and there are no additional mods to the car. The only thing that has happened to the car is it's had it's 60k service including Cam belt and two new tyres on the front.

Seems strange. Here's my best guesses:
1) Air filter needs changing/replacing (Not sure if that could affect fuel consumption! Can it?)
2) Lambda is on it's way out. 62k miles seems to be an exception for the longevity of these items. That said though, if that was dying, wouldn't my AFR show un usual readings?

Thoughts anyone?

 

my mileage dropped off just before my lambda sensor needed changing.

 

It should be noted that you were getting approx 20 mpg and now you're getting approx 17. (Assuming 12 gal used per tank) It's not an enormous change yet, so
your AFR may not look "off" if the sensor is just beginning to die.

On high RPM and high boost the car runs open loop and filthy rich. There's usually not enough range in a standard lambda sensor to show that much difference here, unless the sensor is really dead. You may see the gauge not illuminating the very top LED to start with.

Under cruise, the lambda will look normal, but the actual AFR will be richer than it should be, as the sensor is instructing the car to fuel more to reach an incorrect target. (Again, assuming a "just beginning to fail" sensor. - if the sensor were very dead, then the car couldn't meet the fuelling target, and the AFR gauge would show lean) This is where most of the fuel economy seemed to be lost on my car when the lambda sensor was failing.

Spark plugs and coils can affect consumption too. I'm losing a couple of MPG while I wait for my new coil packs

 

Mikey, its your lambda sensor. Your afr would show rich, but probably off the scale rich.

Steven

 

The expensive one then lol

Always the bloody case int it?

Shouldn't be the plugs, they got changed 2k ago. So definately not the air filter then?

What happens if ya airfilter is inefficient then. (As in not letting enough air through, not as in letting rubbish through)

Mikey

 

Just as an after thought, On long motorway stints, my AFR just dies. It shows no readings at all, even with WOT. I'm assuming again that the lambda is getting really hot and because the car doesn't use it at high rpm/cruise conditions it just ignores it. Is that about right or is this potentially another pointer to Lambda death?

Mikey

 

Yep

Lambda on its way out

 

Yah Fackin' Hoo! £150 notes is that about right or can you get em tested off of scrapped cars and buy em second hand?

Mikey

 

Mikey

You can get a 'cheap' universal one from Halfrauds L300 Oxygen Sensor 25 quid , but you will need to swap the connectors over, (which isnt that bad to do) I have a MY00 and ive been using the halfords one for about 20 k miles

S

 

Nice By swap connectors i presume you mean bin the one it comes with and attach the oe one?
How much Gaffer tape will i need lol

Mikey

 

Given that subaru have just cut the prices on a lot of parts its worth contacting them. Or Try BR Developments www.brdevelopments.com they might have some. £100 should see you with one i guess.

 

Yep thats what I mean, you cant solder the wires, as the solder wont stick, but you could crimp them, or other joining mechanism

S

 

Try here

Cats Direct

HTH

Mark
UK Twin Turbo Legacy Register

 

Cheers GTB, learnt more about Lambdas in 5 mins on that site than 3 years on here lol

So has my MY00 got a 1,2,3 or 4 wire sensor?

I could go and look but it's hammering down with rain lol

Mikey

 

3 wire, 2 black and one white, or two white, one black, basically its the exact same as the halfords one