Ford Fiesta ST
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#371392 - 27/11/11 09:43 PM What could be wrong...
ringo747 Offline


Registered: 04/11/08
Posts: 34
Loc: N. Ireland
Hi chaps, not a frequent poster but here goes.

Usually when I fill up the dashboard indicator thingy estimates around 300 miles until empty. Now when I fill up it estimates around 200. When I am driving I reset the mpg readout and it always goes back to a normal value.

The other thing I noticed is that the fuel level indicator seems to drop too quickly. Apart from the obvious check for holes in the tank, what else could be the problem?

I noticed too that sometimes the outside air temperature readout is around 15degrees or so when it is absolutely freezing outside. Is this value likely to affect the ECU settings for mixing fuel? If so I'd have expected the mpg readout to drop accordingly. Not sure how accurate the temperature is - it is fine sometimes and it usually detects when it is freezing and gives me ice warnings.

It's a weird one.

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#371393 - 27/11/11 09:46 PM Re: What could be wrong... [Re: ringo747]
H47PER Offline


Registered: 23/11/09
Posts: 4599
Loc: sheffield
maybe worth a pop into a garage for a diagnostics machine if you dont mind the expense.

how many miles are u actually getting out of a tank
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#371394 - 27/11/11 09:51 PM Re: What could be wrong... [Re: H47PER]
ringo747 Offline


Registered: 04/11/08
Posts: 34
Loc: N. Ireland
I can't afford one of those £60+ tests that might show nothing! Can you buy the testing equipment fairly cheap that would do all fords?

Tonight when I checked the readings were something like:

Distance to empty: 30
Miles done since last reset: 177
Mpg: Somewhere around 28.

I'm not sure if those figures even add up! I don't believe the tank is leaking but could there be a leak at the fuel hose ONLY while the car is running?

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#371395 - 27/11/11 09:57 PM Re: What could be wrong... [Re: ringo747]
Burn4 Offline
Site Supporter

Registered: 25/05/10
Posts: 8576
Loc: Birmingham, England
wouldn't you smell petrol/ there would be a puddle on your drive if this was the problem?
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#371396 - 27/11/11 10:04 PM Re: What could be wrong... [Re: Burn4]
ringo747 Offline


Registered: 04/11/08
Posts: 34
Loc: N. Ireland
That's why I don't think the tank is leaking! I wonder could it be leaking only once the engine has started and I drive off.

Normally the readout would say around 300 miles to empty when I fill up. Normally I'd get over 31mpg with motorway driving (K&N fitted helps).

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#371397 - 27/11/11 10:06 PM Re: What could be wrong... [Re: Burn4]
nosnow3 Offline


Registered: 11/06/09
Posts: 1930
you would defiantly smell a petrol leak...

is the car due a service i noticed on my 1.4 its dropping accordingly over the past 2 months. i was averaging around 37mpg and i suddenly decided to carm it down a little for a weeks it crept upto 38 - 39mpg but ive gone back to normal and its slowly dropping is around 34mpg now, this is with similar driving every week. my oil is in need of changing as it was done 8 months ago and i'd usually get it done every 6 as that's where i begin to notice an MPG drop

ive got 3 days of driving to worksop and back for doing a few tests to finish my apprenticeship off, its an hour each way so my MPG should pick up abit as it will be early mourning driving and with a relitivly simple journey, so hopefully the MPG will come back up for me, a service is still due for me none the less


Edited by nosnow3 (27/11/11 10:08 PM)

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#371398 - 27/11/11 10:10 PM Re: What could be wrong... [Re: Burn4]
STASON Offline


Registered: 05/01/11
Posts: 5720
Loc: UK, Essex
if the cars cold dont expect miracles on the old mpg i get something like 16mpg until the temp gauge reads 20 degrees where it starts gradually climbing.

the problem your describing is not normal by any means to really get to the bottom of it all your need to ignore the dashboard and work it out your self.

Fill the car up tomorrow (monday to a full tank) and clock the miles to zero.

the tank holds 42 litres in total.

which is proximately 9.23 gallons -1.50 which is the reserve light so 7.73 gallons.

What your need to do is drive as you normally would drive and drive it until the orange light.

Check how many miles you have done and then divide it by 7.73 which should give you your rough average miles per gallon.

once we can determine what is your actual mpg we can move on from there as it sounds that your car is over-fueling which could mean previous map on your ECU or something else.

mine last time i checked

360 miles since last fill up

divided by 9.23

39mpg flat.


Edited by STASON (27/11/11 10:16 PM)

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#371399 - 27/11/11 10:11 PM Re: What could be wrong... [Re: nosnow3]
ringo747 Offline


Registered: 04/11/08
Posts: 34
Loc: N. Ireland
It is due for MOT in new year so will get her checked then. I had the oil changed a few months ago coz it was leaking oil. What else would cause such a drastic increase in consumption? Surely mpg decrease from 31-28 wouldn't make me get 70 less miles per tank!

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#371400 - 27/11/11 10:17 PM Re: What could be wrong... [Re: ringo747]
nosnow3 Offline


Registered: 11/06/09
Posts: 1930
sorry stason its 45 litres

a 3mpg decrease can be expected with lack of service because you begin to lack power which means more on the go pedal

ever watch the topgear episode where they tryed to make a renault people carrier (meg something or other) as fast as an EVO X

the bhp was down something like 30bhp they gave it a service and it was almost back to origanel power...

give it a good service, and check no brake's are binding, i know when i did an ST rear axle swap so i could have discs one of the calipers on the new axle to fit was seized and it was notably obvious it had been on for awhile as the disc and pads are now almost useless (something i need to get round to servicing) all i did was push the piston back in and use the brake pedal to push it back out a few times and it worked it self free

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#371401 - 27/11/11 10:19 PM Re: What could be wrong... [Re: ringo747]
ringo747 Offline


Registered: 04/11/08
Posts: 34
Loc: N. Ireland
STASON,

I did exactly that last week and tonight the orange light came on while showing I had completed 170 miles. Something not right there!

What exactly is over-fuelling in technical terms?

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#371402 - 27/11/11 10:21 PM Re: What could be wrong... [Re: ringo747]
nosnow3 Offline


Registered: 11/06/09
Posts: 1930
over fuelling is too rich

there is an optimum amount of fuel to air, too much or not enough can cause bad effects on the engine. look up air to fuel ratio. i think it needs to be 14.7

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#371403 - 27/11/11 10:22 PM Re: What could be wrong... [Re: ringo747]
H47PER Offline


Registered: 23/11/09
Posts: 4599
Loc: sheffield
you noticing any blue/white smoke heavily puffing out of exhaust?
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Chuck Norris is never late, the world is just early!!

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#371404 - 27/11/11 10:26 PM Re: What could be wrong... [Re: ringo747]
STASON Offline


Registered: 05/01/11
Posts: 5720
Loc: UK, Essex
can be anything possible causes, faulty lamda sensor, airflow meter, wiring, ecu fault, air leak, faulty injector list goes on.....

this is why as someone already suggested getting it checked out by a diagnostic machine should read any faults and narrows the problem down.

170 miles to a tank is really bad.

surely it must feel slow or crappy to drive, does your car feel lumpy on the throttle, and does it hesitate on the throttle?

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#371405 - 27/11/11 10:26 PM Re: What could be wrong... [Re: H47PER]
ringo747 Offline


Registered: 04/11/08
Posts: 34
Loc: N. Ireland
No I have noticed nothing unusual at all except that my fuel isn't lasting me long enough!

There are no faults or anything on the dash. No clues at all.

Would a faulty temperature sensor affect the mixture? Some nights it is fairly nippy outside yet the dash is showing 20 degrees. The bumper was replaced earlier this year after I hit a dog. I think the sensor is attached to bumper. Would it be dodgy?

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#371406 - 27/11/11 10:31 PM Re: What could be wrong... [Re: ringo747]
STASON Offline


Registered: 05/01/11
Posts: 5720
Loc: UK, Essex
theres got to be a link between your sensors mate because the car is over fueling (or lets presume so by what you said)

what does the temperature gauge for your engine read after driving around mate does it sit neat or near 60 degrees?


Edited by STASON (27/11/11 10:31 PM)

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