Really really bad fuel consumption

[Peter Gidden]

This issue is 99% likely to be O2 sesnor.

[ashyk36]

I averaged about 35MPG motorway driving over summer.
Regarding the issue about high cold idle, this is normal so long as it comes down once the engine is warmed up. But because it is idling slightly lumpy, i'd suggest possibly a lambda sensor would be at fault. Which would explain your fuel consumption.
Are you able to smell overfuelling at all?

My car also has a slight whistle under acceleration, but i've not noticed any loss in fuel consumption. It's probably a leak from around the airbox or piping to the throttle body. That shouldn't cause high fuel consumption though.

I can definitely smell fuel when I turn the car on from a cold start. I will have a look later on to see if this is still the case when the car is warm

[ashyk36]

Sticky/siezed calipers?
Could this also help to lower your mpg?

Been checking the temp of my wheels for the last few days after a half on hour drive to/from work.

I can confirm that I am 99% sure that binding calipers are not an issue. I cannot feel any 'extra' heat on the wheel. The wheel is pretty much cold.

[ashyk36]

If your mpg is that bad I would check that your thermostat isn't stuck open as well. Does the coolant temperature gauge behave normally?

The gauge has never shown signs that it is not working correctly. The needle when warm always stays just below the half mark. I have never seen the gauge even go up to half way since I have had the car.

[ashyk36]

This issue is 99% likely to be O2 sesnor.

Would this show up on a diagnostics? Or would I need to just change the sensor and then find out later if it has worked or not?

[Peter Gidden]

This issue is 99% likely to be O2 sesnor.

Would this show up on a diagnostics? Or would I need to just change the sensor and then find out later if it has worked or not?

We'd 'scope the sensor output before removal. An analogue voltmeter can be used too.

[ashyk36]

I think the 'whistle' sound is the alternator. I have checked for air leaks and I cannot find any. I am now going to check the green coolant sensor.

Does anybody know off the top of their head where in BGB it says how to remove and test the green coolant sensor?

I have found the green coolant sensor underneath the throttle body (as below) but I have read that this sensor is normally at the bottom of the coolant bottle, can any body shed some light on this for me please?

https://skydrive.live.com/redir?resid=B ... oto%2c.jpg

[cvega666]

haha, 220 miles to a tank, my turbo with very rich fueling did better than that.

[Peter Gidden]

other stuff

So you've confirmed the O2 sensor is working correctly?

[ashyk36]

Just a quick update. Have changed my green coolant sensor and I know get decent fuel consumption. I have calculated I get just over 30mpg in the city.

Thank you to all that have helped me! Appreciated! 1 happy forum member