General Seicento 1.1 MPI excessive fuel consumption

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General Seicento 1.1 MPI excessive fuel consumption

dx90

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What would cause excessive fuel consumption, but show no codes?

Car starts first turn of the key every time and is running good. The idle is smooth as well.

I have done an oil and oil filter change. Air filter change (original). Replaced the o-ring and breather pipe to the air filter. New cam belt, water pump and idler bearings. Also gave it a good coolant flush and change.

It also passed the MOT emissions recently with no problem.

Thanks
 
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Sorry should of put that. About 20 mpg.
 
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Apart from fuel leak (you passed MOT, so I assume it is not the case):

- shot lambda sensor(s) (hard to believe, MPIs have two and should see that one is not in line with the other)

- shot coolant temperature sensor

- shot MAP sensor

- thermostat stuck open

- very heavy foot :D

(Depends also what your driving pattern is, I get very high consumption on my GP driving only up to 3 km at a time in city traffic, and this is normal).
 
What would be considered good? Or average? I get around 40ish, sometimes just over and under. Mines been decatted and pod filter.
 
I've started to look at and trying to understand STFT and LTFT. Is there any standard readings for this engine that I should be comparing to?

This seems to be the only path to take to see what's really going on with this engine and it's excessive fuel consumption.

Thanks
 
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No from half a tank to half a tank. I have refilled to a full tank now and will come back with the results. I only do short journeys.

Thanks
 
I put £10 in every 80 miles what is be about 40mpg i think. Upi are working it out correctly as it 4.54lt to the gallon. Dont get mixed up with the US gallon. Also have you not long got this car? If so remember is a small tank at around 38lt so it would seem you are using fuel quicker and also if like mine the light comes on at the 1/4 mark what i think the book says is almost a gallon.
 
Filed the tank up twice now and run it until the light comes on. Both times it gave an average of 170 miles to a tank of fuel. That's around 20 mpg. It is all local driving.

Any advice is welcome.

Thanks
 
Got any idea on what the cars mpg driving it local should be?

Thanks
 
Filed the tank up twice now and run it until the light comes on. Both times it gave an average of 170 miles to a tank of fuel. That's around 20 mpg. It is all local driving.

Any advice is welcome.

Thanks

I did read somewhere that when the light comes on you still have almost a gallon so that would take you up to 22 mpg :D Nah your right, that is ****. Think i am closer to 40mpg running round town and a few country road miles. So any sign or a fuel leak? It may only happen when running or higher reving due to pressure. Look round the injection system while someone is sitting the car at, sat 3000 rpm as you must be leaking. How about the filler cap, any mess from spillt fuel running down the body as the cap seal may be gone.
Also fuel lines under the car. Mine are corroded and an advisory to change on last MOT. They can rot from the inside out and the wet fuel on the outside evaporated fast making it hard to spot. I had this on an old astra fuel pump. The high MPG was driving me mad.
 
I did read somewhere that when the light comes on you still have almost a gallon so that would take you up to 22 mpg :D Nah your right, that is ****. Think i am closer to 40mpg running round town and a few country road miles. So any sign or a fuel leak? It may only happen when running or higher reving due to pressure. Look round the injection system while someone is sitting the car at, sat 3000 rpm as you must be leaking. How about the filler cap, any mess from spillt fuel running down the body as the cap seal may be gone.
Also fuel lines under the car. Mine are corroded and an advisory to change on last MOT. They can rot from the inside out and the wet fuel on the outside evaporated fast making it hard to spot. I had this on an old astra fuel pump. The high MPG was driving me mad.

Checked filler cap and that seems to be sealing OK.
Is the tank and fuel lines on the Seicento a sealed pressurised system when the pump is running and should I feel suction taking the cap off after a run?

I'll check around the injectors tomorrow as my son is out in the car this afternoon.
I have never smelt any petrol in the cabin or outside the car.

I will have a good look around the tank and the fuel lines with the engine running tomorrow at the same time as checking for leaking injectors.

Thanks for your advice. (y)
 
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The tank may have slight pressure in it but not a great deal. It has an air vent as if no air get into it no fuel will flow even the pump would struggle eventually but that would cause poor fuel delivery not poor consumption. What is the car millage, does it smoke or burn oil?
 
No smoke and never burns any oil. It has 57000 miles on the clock. Starts first turn of the key winter and summer, never fails.
 
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