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fuel consumption enigma
Hello,
I have been searching to find info on this problem. The car is a Mitsubishi Space Star 1.3 16 V 1999. Normal consumption averaged 6.2 l / 100 km. After a while, but suddenly, fuel consumption lowered, starting at 5 l to even 4 l / 100 km. And this on average and instantaneous rate. A fill up at the gas station confirmed the figure from the onboard computer. Does anyone know how this consumpton is calculated, and could this mean a sensor has gone faulty ? The odometer has no significant fault, only 10 %, which would not explain the problem. Any help warmly appreciated, Regards, Carl |
In article . com>,
says... > Hello, > > I have been searching to find info on this problem. The car is a > Mitsubishi Space Star 1.3 16 V 1999. > > Normal consumption averaged 6.2 l / 100 km. After a while, but > suddenly, fuel consumption lowered, starting at 5 l to even 4 l / 100 > km. And this on average and instantaneous rate. <rest snipped> Causes of poor fuel consumption include (in no particular order): 1) Failed / failing lambda sensor (also known as oxygen sensor). See http://www.picotech.com/auto/lambda_sensor.html 2) Incorrect tyre pressures 3) Failed thermostat - does the engine get up to operating temperature OK? 4) Failed temperature sensor - if it gets to the right temperature, does the engine managament system know it? 5) Binding brakes - do any of the wheels feel far hotter than they should? Does the car "Lurch" to a halt, or gently glide to a stop? 6) Fuel leak - should be obvious by the smell! (But I guess if the computer is showing poor economy this is not the case for you..) and finally, and most obviously 7) Forgetting to remove roof-rack, trailer or caravan ;-) Ian -- Ian Riches Bedford, UK |
"Ian Riches" wrote
> > Normal consumption averaged 6.2 l / 100 km. After a while, but > > suddenly, fuel consumption lowered, starting at 5 l to even 4 l / 100 > > km. And this on average and instantaneous rate. > > Causes of poor fuel consumption include (in no particular order): > ... In this case it's not poor fuel consumption, it's an exceptional good fuel consumption. > > Does anyone know how this consumpton is calculated, > > and could this mean a sensor has gone faulty ? If a fill up at the gas station confirms the onboard computer, it's probably not faulty. Don't touch the perfectly running system! Thomas |
Ian Riches ) gurgled happily, sounding much like they
were saying : >> Normal consumption averaged 6.2 l / 100 km. After a while, but >> suddenly, fuel consumption lowered, starting at 5 l to even 4 l / 100 >> km. > Causes of poor fuel consumption include (in no particular order): Umm, Ian... 6.2l/100km is 45mpg 5l/100km is 55mpg 4l/100km is 70mpg. > And this on average and instantaneous rate. So this is the economy that the trip computer's reporting? Personally, I think the computer's lying through it's teeth... (I presume it isn't *really* doing 70mpg? If it is, find the problem, and bottle it. You'll make your fortune.) |
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Ian Riches ) gurgled happily, sounding much like
they were saying : > not being used to people complaining about *improved* fuel economy <snort> A definite rarity... |
"carl" > wrote in message ups.com... > Hello, > > I have been searching to find info on this problem. The car is a > Mitsubishi Space Star 1.3 16 V 1999. > > Normal consumption averaged 6.2 l / 100 km. After a while, but > suddenly, fuel consumption lowered, starting at 5 l to even 4 l / 100 > km. And this on average and instantaneous rate. > > A fill up at the gas station confirmed the figure from the onboard > computer. > > Does anyone know how this consumpton is calculated, and could this mean > a sensor has gone faulty ? > > The odometer has no significant fault, only 10 %, which would not > explain the problem. > > Any help warmly appreciated, > Pop your spark plugs out and have a look at them to see if there are signs of it running lean. |
I'd check the computer by keeping a record of the amount of fuel purchased and the odometer reading each time you buy gasoline and do a calculation by hand. I keep a notebook in the car in which I record the money spent on gas for my personal budget, and the amount and milage to compute fuel consumption. I have a record of every gas purchase going back to April 1989 when I purchased the car new. I understand it's more accurate if you fill up the tank each time but I don't. I also keep a record of all maintenance in the notebook. :) "carl" ) writes: > Hello, > > I have been searching to find info on this problem. The car is a > Mitsubishi Space Star 1.3 16 V 1999. > > Normal consumption averaged 6.2 l / 100 km. After a while, but > suddenly, fuel consumption lowered, starting at 5 l to even 4 l / 100 > km. And this on average and instantaneous rate. > > A fill up at the gas station confirmed the figure from the onboard > computer. > > Does anyone know how this consumpton is calculated, and could this mean > a sensor has gone faulty ? > > The odometer has no significant fault, only 10 %, which would not > explain the problem. > > Any help warmly appreciated, > > Regards, > > Carl > -- ------------------------------------------------------------------------------ William R Watt National Capital FreeNet Ottawa's free community network homepage: www.ncf.ca/~ag384/top.htm warning: non-FreeNet email must have "notspam" in subject or it's returned |
The fuel consumption is normally calculated with the injection time on
this injector by the ECU. The fuel consumption is given as frequence signal to the computer. This is most of the system anyway. A really good fuel consumption can mean a lot of thing, from the ecu calculating wrong to a computer problem. As your engine is still running fine, I do not thing that the ECU is gone. I will personnaly tip on a signal problem betwwen the ECU and the computer. This could be chekced by any good repair shop. Another possible problem is the mileage of the injectors. In some cases, large mileage injector tends to inject far much more than normal. Therefore the ECU will correct the injection volume by dropping the injection time, reducing the calculated fuel consumption. However, you will see it on your gas exhaust measurement, normaly the Nox, COx and HC are exploding ! Well I will recommend you to have your electric system checked ! Regards Jerome Douay www.Team74.com |
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