What to check - Fiesta ST

ringo747 · 7 Nov 2011 at 16:51

Usually when I fill up the dashboard indicator thingy estimates around 300 miles until empty. Now when I fill up it estimates around 200. When I am driving I reset the mpg readout and it always goes back to a normal value.

The other thing I noticed is that the fuel level indicator seems to drop too quickly. Apart from the obvious check for holes in the tank, what else could be the problem?

I noticed too that sometimes the outside air temperature readout is around 15degrees or so when it is absolutely freezing outside. Is this value likely to affect the ECU settings for mixing fuel? If so I'd have expected the mpg readout to drop accordingly.

It's a weird one.

PiKe · 7 Nov 2011 at 16:55

Outside temp readout and the sensor the engine uses are most likely completely different.

ringo747 · 7 Nov 2011 at 17:04

I have a funny feeling on the ST it is the same thing but can't be sure.

GeX · 7 Nov 2011 at 18:15

ringo747 said:
I have a funny feeling on the ST it is the same thing but can't be sure.

It's a very stupid design if the exterior temperature and inlet air temperature are the same thing. I doubt they've done that. The IAT will be combined with the MAP and be in the inlet tract.

Cold weather means it'll use more fuel, what MPG is showing?

ringo747 · 7 Nov 2011 at 18:19

It's showing about 30mpg which is the normal for motorway driving really. There doesn't appear to be any obvious fuel leaks so I'm not sure what's up.

Locky · 7 Nov 2011 at 18:21

ignore.

Rybo89 · 7 Nov 2011 at 18:25

Never trust the on-board computer, especially a Ford one.

Laurio · 9 Nov 2011 at 16:13

Rybo89 said:
Never trust the on-board computer, especially a Ford one.

Yep dont trust what its telling you is true, i have similar issues with my ST.

ringo747 · 9 Nov 2011 at 16:28

I disconnected the battery for a bit and now it seems a bit more like the thing.

Laurio · 9 Nov 2011 at 16:48

Are you a member of FiestaSTOC?