A6 Fuel consumption

[Ian Brown A6]

Hi there. We have a A6 1.9 diesel 2003. The fuel consumption went really bad and the temperature gauge stopped working. I was told that the ECU would be over fueling the engine as it will think the engine is cold. I have replaced the temperature sender and the thermostat. The fuel gauge is now working but the fuel consumption is not where it should be. Do i need to re set anything for the ECU to function properly? Any help would be great. Thanks. Ian    

[Magnet]

Hello Ian,

Please don’t quote me on this, but do your own research.

Some (many?) marques are fitted with not only a coolant temperature sender, which controls the temperature gauge readings, but also with a coolant temperature sensor (CTS) which signals the ECU to control the mixture depending on the coolant temperature. Yours fitted with this system?? These are generally in close proximity - if fitted. 

Of course, your high fuel consumption may have nothing to do with either of these. 

Depending on what you consider to be ‘high’ it is likely you would benefit from some basic investigation via. a trusted local diesel specialist. 

Kind regards,

Gareth.

[Rudis_Dad]

If the ECU is over-fuelling the engine you'll get a lot of black smoke out of the exhaust every time you put your foot down. You really need to find a diesel specialist who will be able to diagnose and cure this

Don't rely on the consumption figures displayed on the dash, especially if the fuel gauge isn't working properly - they're woefully optimistic at best.

If you want an accurate picture of your fuel consumption, do it long hand - knowing how to use Excel can help here!

Next time you fill up, reset the trip meter to zero; at the following fill up, fill the tank to capacity. Note what mileage is displayed, and make a note of the number of litres purchased (or the total cost and cost per litre). Reset the trip to zero again.

To work out your actual fuel consumption in mpg, proceed as follows -

1. Work out how many gallons you've bought - divide the total price you paid by the price per litre, to obtain the number of litres purchased. Divide the result by 4.546 - this will give the number of gallons that you have bought. (Example - £50 total divided by £1.249 = 40.03 litres; 40.03 divided by 4.546 = 8.81 gallons).

2. Divide the number of miles covered since the last fill up, by the number of gallons you've just purchased - this will give you your actual mpg. (Example - 300 miles divided by 8.81 gallons = 34.1mpg)

You'll find that this figure will vary quite a lot from what's displayed on your dash.

Also, pay attention to your tyre pressures. An under-inflated tyre can really drag your consumption figures down