Runs great but 10mpg ?, I Replaced the alternator with a motorcraft all is good but battery light comes on and stays on,?

[Browning]

I ran the car for over a year with 4 of the diodes b but it was making enought power to run the car at 12.5v but now exceserery s like fan blower ect so I replaced the alternator with Ford original one a smart one all is good now ,but the battery lite comes on about 10 sec.latter! Check out the output and all is good@13.6v+- but consistent. Now my gas mileage is off the chart at 10mpg around town 24mpg on hiway ,its a2000 fual injections, automatic transmission ,78000 mil runs good no signs Of exsess fuel in the tail pipe? I reset the ecu as best I could ! 1 hr battary disconnected started it no thradle 4 15min no change ? What's up I need ideas! can I reload the oprating system for the computer? Hit me back thanks lbcolarry@gmail.com

[StephenFord]

I'm curious, is the mileage you quote taken from the cars 'computer', or, have you actually brimmed the tank, driven a bit, and refilled calculating the actual MPG rather than what a computer chip says?

[Hearsepilot]

If you've reset the ECU it will take a while for it to re-learn the fuel trims and the gearbox shift points. You could use a OBD device to reset the gearbox, the engine will sort itself eventually but you'd be better off using OBD to reset the misfire parameters etc

[Browning]

On 10/8/2021 at 1:08 AM, StephenFord said:

I'm curious, is the mileage you quote taken from the cars 'computer', or, have you actually brimmed the tank, driven a bit, and refilled calculating the actual MPG rather than what a computer chip says?

Yes I mileage decided by gal fual many times, on The hiway I got 24mpg 390mile drive . The quote is 38mpg hiway! 

 

[Browning]

And now my electric system is right,and I reset the ecu to correct the mpg,but same results are accurring or no change. Tail pipe is running clean no signs of exsess fuel use?  One more thing battery light is coming on 20sec. After start ! 

[unofix]

Hello Larry, are you in America ?

[Hearsepilot]

3 hours ago, Browning said:

And now my electric system is right,and I reset the ecu to correct the mpg,but same results are accurring or no change. Tail pipe is running clean no signs of exsess fuel use?  One more thing battery light is coming on 20sec. After start ! 

Do you have any means of checking the battery voltage 1st with the engine off and 2nd with the engine running before the light comes on finally 3rd with the light on?

[StephenFord]

7 hours ago, unofix said:

Hello Larry, are you in America ?

Sound observation - 'highway'

[unofix]

On 10/8/2021 at 4:04 AM, Browning said:

Now my gas mileage is off the chart at 10mpg around town 24mpg on hiway

Are we talking about a UK gallon of Petrol or a USA gallon of Gasoline ?

UK 1 gallon = USA 0.833 gallon

[DaveT70]

I take it it's a MK2 Focus (or the daft thing you got in the USA after the MK1) and the 4 speed auto.

1st thing I would do is make sure the car is properly serviced;

Good new oil & filter

New (Correct) spark plugs and HT leads

New Air Filter

Clean the MAF sensor

Clean the throttle body

then, ensure the transmission fluid is good, if not change

Then see how you get on.

To get real world fuel economy figures:

Fill fuel tank to first click

Reset trip mileage

Drive as normal for about 100 miles

Go back to same pump and fill back to first click

Work out how many miles you did on the amount of fuel you had to put back in to first click on Pump.

That's your true MPG

[StephenFord]

1 minute ago, DaveT70 said:

To get real world fuel economy figures:

Fill fuel tank to first click

Reset trip mileage

Drive as normal for about 100 miles

Go back to same pump and fill back to first click

Work out how many miles you did on the amount of fuel you had to put back in to first click on Pump.

That's your true MPG

Oh dear, are you suggesting that our American cousins don't know how to measure their fuel consumption?? LOL 🤣

[DaveT70]

40 minutes ago, StephenFord said:

Oh dear, are you suggesting that our American cousins don't know how to measure their fuel consumption?? LOL 🤣

They can't do.

It looks like he's going off the fuel computer

[Hearsepilot]

7 hours ago, StephenFord said:

Sound observation - 'highway'

Not so sound observation, he typed "hiway"

[StephenFord]

4 minutes ago, Hearsepilot said:

Not so sound observation, he typed "hiway"

If he's American, poor spelling is to be expected! For goodness sake, they don't even put a 'U' in colour! LOL 🤣