97 Windstar MIL Codes P0171 P0174

Fuel mixture is going lean.... from the look of the skimpy freeze frame data it SEEMS to be happening when you are driving normally rather than at idle... (heavy on the seems). Based on this, we should be able to rule out vacuum leaks - at least for now... but check fuel trims at idle all the same - should be "tight to zero"...

Fuel pressure should be checked.. use a gauge and check the pressure while driving. Checking fuel pressure at idle for a concern such as this is a waste of time.

Checked the TPS it seems ok the graph looks good.

Used some in tank fuel cleaner and drygas, added more fuel to no avail, seems to run good, no loss of power nor misfires.

One time the MIL lit right at the station after fueling.

Here is a cut and paste of the Autotap scanner results:

AutoTap Diagnostic - Version 3.10 Date: 11/25/2009 6:09:02 PM

Check Engine Light: ON

Time Since Codes Cleared:

Oops put this in the wrong thread

Thanks Jim,

I will take your advice.

What is normal pressure at Highway speed? and Idle?

What is the normal range?

Thanks again Joe

Checked the TPS it seems ok the graph looks good.

Used some in tank fuel cleaner and drygas, added more fuel to no avail, seems to run good, no loss of power nor misfires.

One time the MIL lit right at the station after fueling.

Here is a cut and paste of the Autotap scanner results:

AutoTap Diagnostic - Version 3.10 Date: 11/25/2009 6:09:02 PM

Check Engine Light: ON

Time Since Codes Cleared:

Fuel pressure spec is 30 to 45 PSI.... Important to remember.... the system is looking for a specific fuel pressure drop across the fuel inject - This pressure drop gives the spray pattern it's best atomization and it's best spray pattern. The requirement for this specific pressure drop is why the fuel pressure regulator has a vacuum line (which, on many Windstars, needs to be inspected closely dues to swelling/poor sealing).

When manifold vacuum is high ( > about 15 inches ) we expect to see fuel pressure at the low side of the "window". When manifold vacuum is low (as when under hard acceleration) we expect to see fuel pressure at the high end of the window.

As a rule, lean codes do not usually set until adaptive fuel strategy (long term fuel trims) has reached about +25%. Most vehicles can operate at this extreme with no apparent drivability symptoms.

It is entiurely possible that a badly restrict fuel filter *may appear* to be the cause. In my humble experience, if the vehicle has been operated with a badly restricted fuel filter long enough to generate a lean mixture code, fuel pump failure is imminent...

HTH

Thanks Jim,

I will take your advice.

What is normal pressure at Highway speed? and Idle?

What is the normal range?

Thanks again Joe

Checked the TPS it seems ok the graph looks good.

Used some in tank fuel cleaner and drygas, added more fuel to no avail, seems to run good, no loss of power nor misfires.

One time the MIL lit right at the station after fueling.

Here is a cut and paste of the Autotap scanner results:

AutoTap Diagnostic - Version 3.10 Date: 11/25/2009 6:09:02 PM

Check Engine Light: ON

Time Since Codes Cleared:

Thanks Jim, I found the problem it WAS a vacuum leak.

Thanks for the detailed info. you are the reason I get better answers on newsgroups than any other place.

When manifold vacuum is high ( > about 15 inches ) we expect to see fuel pressure at the low side of the "window". When manifold vacuum is low (as when under hard acceleration) we expect to see fuel pressure at the high end of the window.

As a rule, lean codes do not usually set until adaptive fuel strategy (long term fuel trims) has reached about +25%. Most vehicles can operate at this extreme with no apparent drivability symptoms.

It is entiurely possible that a badly restrict fuel filter *may appear* to be the cause. In my humble experience, if the vehicle has been operated with a badly restricted fuel filter long enough to generate a lean mixture code, fuel pump failure is imminent...

HTH

Thanks Jim,

I will take your advice.

What is normal pressure at Highway speed? and Idle?

What is the normal range?

Thanks again Joe

Checked the TPS it seems ok the graph looks good.

Used some in tank fuel cleaner and drygas, added more fuel to no avail, seems to run good, no loss of power nor misfires.

One time the MIL lit right at the station after fueling.

Here is a cut and paste of the Autotap scanner results:

AutoTap Diagnostic - Version 3.10 Date: 11/25/2009 6:09:02 PM

Check Engine Light: ON

Time Since Codes Cleared: