I have a 2002 STI Prodrive which I have owned for just over a month. I noticed that I was getting around 15-18mpg even when driven with a light right foot.

When it was serviced last week they diagnosed that the front Lambda sensor was running lean and as such it was overfueling. Had this changed on Saturday (it still had the original one on from new!!). I have not yet done enough miles to see if there is an improvement in MPG yet. However I was suprised by some other improvements.

It is now running at a steady 500rpm on idle, before it was running between 750-950 and occassional pulsing higher. Pick up is much smoother, even from lower down and off boost. It seems to be boosting harder and "cleaner" than before. I dont know how but it also sounds better as well.

Maybe some of these improvements are in my head but that is my first impression after a spirited 40 mile drive back from the garage . Are these improvements expected with a changed lambda sensor or is it just me

 

I think 750 revs is normal (for any car to be honest). Are you getting any backfiring?

15-18mpg is too much though. If you drive light footed, should be pushing easy 30mpg (Ive got an impressive 40mpg in my hatch with 4 people, dogs and suitcases all in toe, but admittedly, I drove like an OAP).

 

No backfire or anything. Sensor is fitted now and spot on I think. I'm hoping to see the MPG improvements once I do a few more miles

 

Did you get the lambda sensor from a main dealer? What was the cost?
I have an idling problem on my car too and was thinking maybe the lambda sensor needs to be changed.

 

Used anauthorised Scooby specialist. (I know u can get them cheaper but I wanted an official one) £280 for sensor plus fitting and vat. Total bill 392 and change, cheers