Glow Plug Change

[MPJones]

I have just changed the glow plugs on my 53 Avensis, taken the negative terminal off the Battery to get rid of the warning lights and the MPG reset to 0.0 as an average, as a result I have managed to get the average upto 44 by careful driving, though before I was getting 50-52 MPG as an average. Does anyone have any ideas as to why this has happened, have I reset something in taking the Battery off? Many thanks.

[Q.S.]

I have just changed the glow plugs on my 53 Avensis, taken the negative terminal off the battery to get rid of the warning lights and the MPG reset to 0.0 as an average, as a result I have managed to get the average upto 44 by careful driving, though before I was getting 50-52 MPG as an average. Does anyone have any ideas as to why this has happened, have I reset something in taking the battery off? Many thanks.

Some engine management systems 'learn' as they go along and tune in to information collected from the sensors, I don't know if this is the case with the Toyota system. If it is, the Battery disconnection will have lost all its previous tuning and will have to 'learn' it all again.

Give it a week or so and see how it pans out.

[MPJones]

I have just changed the glow plugs on my 53 Avensis, taken the negative terminal off the battery to get rid of the warning lights and the MPG reset to 0.0 as an average, as a result I have managed to get the average upto 44 by careful driving, though before I was getting 50-52 MPG as an average. Does anyone have any ideas as to why this has happened, have I reset something in taking the battery off? Many thanks.

Some engine management systems 'learn' as they go along and tune in to information collected from the sensors, I don't know if this is the case with the Toyota system. If it is, the Battery disconnection will have lost all its previous tuning and will have to 'learn' it all again.

Give it a week or so and see how it pans out.

Still reading around 45-46MPG at best, a bit concerned I have reduced my MPG by fitting new glow plugs or would that not be the case. Has anyone any thoughts on this, many thanks.

[Beagh1958]

Glow plugs are purely for aiding with cold start only & as such have no effect on your fuel consumption.

[MPJones]

Glow plugs are purely for aiding with cold start only & as such have no effect on your fuel consumption.

Thanks, so its most probable that I have reset the way the computer converts MPG and so the reading must have been too high to start with.

[caveman_si]

Could also be the due to fuel.

Winter diesel fuel gives lower milage. And since its not been cold until recently suppliers may have held off supplying it to garages. Its a possiblity remote but possible. I know I could see the differnce with my old car.

Another possbility is you knocked something eg fuel line when you fitted the glow plugs, either letting air in or fuel out worth checking.