High fuel consumption

[Anonymous]

filled up last week and put £20 (around 26 litres) in. and i only managed to squeeze 150 miles out of it. i will only get 75 miles out of tenner too. is this normal? and btw i didnt fill up till the needle was right at the bottom and 25 miles with the light on. my last car a puma, could get just over 200 miles to £20...

id say my driving style is 80% economy and 20% givin' it a bit!  s:twisted: :twisted: s:twisted:  

one more thing, when i filled up today, just 10 quids worth, the car felt more resposive then with a very nearly empty tank. Does the 2 suffer from fuel starvation problems on a low tank???  s:? :? s:?

[Anonymous]

I would do the following, clean your MAF, your O2 sensors and reset the ECU, then give it another try.

No it doesn't matter if the fuel is low, to the engine mixture.

[Anonymous]

cleaned the maf and reset the ECU about a month ago

[Anonymous]

The O2's? When i took mine for a emmisions test it was running rich, i cleaned the O2 and it made alot of difference. They carbon up and they sense less so add fuel to richen up even though it's not needed. This then throws the ECU's long term fuel trim out, which only takes a few days to take effect. So your reset a month ago is now back to how it was.

[Anonymous]

ill order meself an o2 sensor socket then mate, cheers

[markiii]

The O2's? When i took mine for a emmisions test it was running rich, i cleaned the O2 and it made alot of difference. They carbon up and they sense less so add fuel to richen up even though it's not needed. This then throws the ECU's long term fuel trim out, which only takes a few days to take effect. So your reset a month ago is now back to how it was.

what did you use to clean them?

[Anonymous]

ive got some wynns caburettor and intake cleaner which i used on the maf, can i use this to clean th o2's aswell?

[Anonymous]

I used the same cleaner that i used on the MAF. Wynns something or other, think it was carb cleaner.   s:? :? s:?

[Anonymous]

Tom:

Why not try measuring your fuel consumption accurately?

Fill your tank to the brim (a bit of a tedious process in the '2 unfortunately)  Record your mileage.  Then drive until the tank is as empty as you like.  Then refill to the brim and work out how many miles you have done.  That way you will know exactly how much fuel you have used for a given distance and can calculate mpg.  

Then, if your figure is not as good as you would expect from others, you can start  to worry.

hth
Andy

[Anonymous]

Tom:

Why not try measuring your fuel consumption accurately?

Fill your tank to the brim (a bit of a tedious process in the '2 unfortunately)  Record your mileage.  Then drive until the tank is as empty as you like.  Then refill to the brim and work out how many miles you have done.  That way you will know exactly how much fuel you have used for a given distance and can calculate mpg.  

Then, if your figure is not as good as you would expect from others, you can start  to worry.

hth
Andy

As a guide figure I did this twice and got 37.1 and 38mpg both times which is the quoted figure (I think). That was giving it a bit too! Don't forget also that as the price of petrol rises you put less in for the same money. I am delighted with that figure as the Volvo used to get about 25 if I was light footed. I checked the instant fuel computer when setting off from lights once. Not booting it, normal acceleration and it read 6mpg!! Didn't check a second time.

[Anonymous]

when putting a tenners worth in, increased petrol prices arn't going to affect it noticably. i know i should be getting 100 miles to a tenner, so my car is definately running rich. i will clean the o2's next weekend and see if that makes a difference

[Anonymous]

i think you might have to reset the ecu when you have done this other wise it will take a week or so to correct

it might be worth doing the maf sensor while your at it just to rule the measuring side out altogether

[Anonymous]

get your bits (ie O2 sensors) cleaned in a ultrasonic tank, they come up like new

[heathstimpson]

I do a lot of commuting runs down the motor way and probably average 34MPG; probably too heavy on the accelerator on the twisties  s:? :? s:?

[Slacey]

You think you've got it bad! I was talking to an RX-8 owner yesterday who says he is lucky to get 18 to the gallon  s:shock: :shock: s:shock:

[SteveJ]

It has been mentioned above in order to get an accurate consumption figure you should fill the tank to the brim - UNDER NO CIRCUMSTANCES SHOULD YOU DO THIS IN A '2

The reason for this is our tank is under vacuum, and when the tank is filled to the point that the fuel is sitting in the filler neck, the vacuum take-off point in the tank is below the fuel level, resulting in large amounts of neat fuel (not just vapour) being drawn through the charcoal canister (black box to the right of the engine bay) and into the intake manifold.

This can have one of 2 effects - the first is the car runs a little rich at idle and the O2 sensors adjust it out at higher revs by backing off the injectors, or worse still the car is grossly over-fueled at idle and will not run. This will be especially noticeable when the car is cold as the O2 sensors are not in the loop along with the cold air temp going through the MAF means that the ECU will go into cold start mode and open the injectors more than it normally would.

The lesser effect (but more relavent to this thread) is that you will end up wasting the first 1/2 gallon of fuel which in turn screws up your calculations.

HTH

[Anonymous]

i do this all the time!  s:shock: :shock: s:shock:    s:? :? s:?    s:shock: :shock: s:shock:  

thanks for the advice i wont fill to the brim any more

is the the same for most cars or just the 2?

how high would you fill the car?

[heathstimpson]

i do this all the time!  s:shock: :shock: s:shock:    s:? :? s:?    s:shock: :shock: s:shock:  

thanks for the advice i wont fill to the brim any more

is the the same for most cars or just the 2?

how high would you fill the car?

So do I; have never noticed any issues before  s:shock: :shock: s:shock:

[heathstimpson]

You think you've got it bad! I was talking to an RX-8 owner yesterday who says he is lucky to get 18 to the gallon  s:shock: :shock: s:shock:

Those Wankel rotary engines have always had a reputation as being extremely thirsty  s:? :? s:?

[Anonymous]

i do this all the time!  s:shock: :shock: s:shock:    s:? :? s:?    s:shock: :shock: s:shock:  

thanks for the advice i wont fill to the brim any more

is the the same for most cars or just the 2?

how high would you fill the car?

So do I; have never noticed any issues before  s:shock: :shock: s:shock:

3rd ditto.

Done this since buying the 2 in March 2002. Never noticed a problem  s:?: :?: s:?:  

Think i need to clean everything, reset the ECU & fill it up less. Then I can see if fuel consumption goes up. Last tank was 28 m.p.g. but, in my defence,  it is all twisties around this countryside  s:!: :!: s:!:

[Anonymous]

I do this also .. I was going to post and ask if the fuel tank was under vaccum as when you undo the cap it makes a whooshing sound.  I have never had any problems touch wood!

[Anonymous]

When i was working down in portsmouth i was driving on the A3 down and back about 120mile round trip, this used to cost me a tenner, now i work about 7 mins from home and i get about 100 mile a week out of 12 - 13 quid. Ive also filled the car to the brim almost once a week .... since i got it and not noticed any problems (granted ive only had it a year) maybe ill not be doing that anymore !

[Darth Paul]

Don't think I've ever filled mine to the 'brim'. I stop when the fuel filler cuts out, and never try and suqeeze more in. Reason for this? So I have a fairly constant gauge to work out fuel consumption.

DP

[Bongo]

What brand of Injection cleaner do you guys recommend? Is there anything else i can do to improve economy? (I've cleaned the MAF, need to get an O2 socket to clean them.)

I've just filled up again and I'm tired of getting ~200 miles from a full tank   s:( s:(

[Anonymous]

Redex or Wynns stuff should be fine. however if you really want to save petrol, dont go over 60mph and dont go over 3k rpm   s:wink: :wink: s:wink: