For a few months my MPG display has been behaving erratically. From moment to moment the reading will take enormous jumps in value. One moment it could be over 100 next it could be 20. Often the display goes blank to three dashes. ( --- ) All the other readings such as external temperature etc seem fine.

Does anyone know what might cause this and if it is expensive to fix ?

That's what it's supposed to do.

For a few months my MPG display has been behaving erratically. From moment to moment the reading will take enormous jumps in value. One moment it could be over 100 next it could be 20. Often the display goes blank to three dashes. ( --- ) All the other readings such as external temperature etc seem fine.

Does anyone know what might cause this and if it is expensive to fix ?

Your looking at the actual realtime MPG and not the average MPG of the trip.....

The average MPG has a little circle with a line through it in the corner of the display. This is the one that only changes avery 10 seconds or so.

Cheers

Dave.

I'm talking about the realtime display.

Up until this problem started the display would function normally. So as I cruised at a fairly constant speed the values would only change a bit. I used to keep an eye on the reading to see if could maximise my mpg.

Now they just shoot up and down, anything from --- to over 100, even though I'm maintaining a fairly constant speed.

Its normal, the --- is infinate mpg, as in your rolling without using gas, or your speed is decreasing. If you keep your rev counter COMPLETELY still, then it wont be irratic, but otherwise its normal to have it jump about.

I'm talking about the realtime display.

Up until this problem started the display would function normally. So as I cruised at a fairly constant speed the values would only change a bit. I used to keep an eye on the reading to see if could maximise my mpg.

Now they just shoot up and down, anything from --- to over 100, even though I'm maintaining a fairly constant speed.

The real time display is supposed to change from --- to anything up to 100-odd..... You might have the peddle at the same position but as the road undulates the engine will be working harder / less as you travel along.... That's why the display will change by such great amounts.

Maybe you had the display on average MPG which only changes by a small amount every 10 seconds or so and have caught the rocker switch and put it onto the real time display.

If there is no

Check the connection to the temperature sensor to fuel metering system (front engine where people put the resistors to fool engine into overfuelling). If a bad connection here everything will work, but readings will be erratic and inaccurate.