Mpg Indicator Fly Up And Down

[marsis]

hi,i want to ask ho know where to check about the sensor location or what more which sent information about fuel consumption to mpg clock...my clock just go up and down all the time,thanks

[ChrisIS200SportTTE]

Hi and welcome. :)

That's what it does. It's just a rough idea not accurate. It's not a computer as in other cars where it gives a accurate mpg read out. It'll go towards 0 when you Accelerate, hover about 30-40 when cruising and drop to 80 when going down a hill or of you take your foot of the throttle completely.

[Dewfallsuk]

The MPG readout is what's called a instantaneous type, it takes various information from the main ECU (speed, engine speed, throttle position ...). Being instantaneous it tends to move through the range, off throttle it shows 80 mpg on throttle it varies 20-40 mpg. In urban driving it can seem to be continually moving, on motorways with steady throttle it will show a more constant reading.

[petayV8]

Yeah its very sensitive and slow to react. Still baffled to think the IS never had a trip computer, even my focus had that

[marsis]

thanks for answers...but even on motorway with constant speed fly up and down...i wonder if that sensor from exhaust pipe read the consumption,if yes maybe is need just a cleaning...

[Dewfallsuk]

thanks for answers...but even on motorway with constant speed fly up and down...i wonder if that sensor from exhaust pipe read the consumption,if yes maybe is need just a cleaning...

I doubt the oxygen sensors would cause this as if they are out of spec they would throw an engine malfunction light.

The Econ meter is part of what Lexus call the combination meter all of its inputs are fed from the engine ECU if the gauge is errant and all other systems are OK I would suspect the gauge. Which would be a replacement instrument panel.

[Lexmanic]

It'll only stay constant if your cruising on absolutely level ground, the slightest gradient will cause it to fluctuate wildly as the cars acceleration compensates to maintain the set cruising speed