High Fuel Consumption, Slight Miss Idling, No Warning Light

[Andrew Haworth]

Hi,
I have a 2006 A3 with an R32 VR6 motor. Fuel consumption has risen sharply lately with a slightly rough idle. I have no indications of an issue on my dash pointing to a problem. I suspect perhaps a temp sensor but the temp indication appears good rising at the normal rate to 90 deg. I have found the two temp sensors, one in the thermostat housing and the other at the bottom of the radiator. Can someone tell me if the ECU uses the one for the gauge or its own sensor? If so which one? Or does anyone else have ideas for this issue or had experience similar the this.
Thanks in advance for any help and advice.
Andy.