'99 XLS Po171 & P0174 codes

My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
has been showing P0171 and P0174 codes for the last several months.
(just came home from college today) He has been getting them reset
(cleared) and after several days they come back on.

Car history: Bought new in '98 and treated well. NO work of any
kind has been required under the hood.

He says it has not affected the performace of his Explorer and it
doesn't have any problems or run rough starting in cold weather. He
also left my Haynes repair manual at school. I think this is the OHV
version? Most if not all of the post refer to the SOHC model.

What should I start to do since he will be home for only a few
days? Any help would be appreciated.

/Richard

"Richard" > wrote in message
...
> My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
> has been showing P0171 and P0174 codes for the last several months.
> (just came home from college today) He has been getting them reset
> (cleared) and after several days they come back on.
>
> Car history: Bought new in '98 and treated well. NO work of any
> kind has been required under the hood.
>
> He says it has not affected the performace of his Explorer and it
> doesn't have any problems or run rough starting in cold weather. He
> also left my Haynes repair manual at school. I think this is the OHV
> version? Most if not all of the post refer to the SOHC model.
>
> What should I start to do since he will be home for only a few
> days? Any help would be appreciated.
>
> /Richard

Here's a place that describes your trouble codes:

http://www.obd-codes.com/p0171

On May 4, 11:57*am, "Ulysses" > wrote:
> "Richard" > wrote in message
>
> ...
>
>
>
>
>
> > * * *My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
> > has been showing P0171 and P0174 codes for the last several months.
> > (just came home from college today) * He has been getting them reset
> > (cleared) and after several days they come back on.
>
> > * * *Car history: *Bought new in '98 and treated well. *NO work of any
> > kind has been required under the hood.
>
> > * *He says it has not affected the performace of his Explorer and it
> > doesn't have any problems or run rough starting in cold weather. *He
> > also left my Haynes repair manual at school. *I think this is the OHV
> > version? *Most if not all of the post refer to the SOHC model.
>
> > * *What should I start to do since he will be home for only a few
> > days? * Any help would be appreciated.
>
> > /Richard
>
> Here's a place that describes your trouble codes:
>
> http://www.obd-codes.com/p0171- Hide quoted text -
>
> - Show quoted text -

Thank you,

I will start looking for vacume leaks and clean the MAF first.
Thanks again.

/Richard

"Richard" > wrote in message
...
On May 4, 11:57 am, "Ulysses" > wrote:
> "Richard" > wrote in message
>
> ...
>
>
>
>
>
> > My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
> > has been showing P0171 and P0174 codes for the last several months.
> > (just came home from college today) He has been getting them reset
> > (cleared) and after several days they come back on.
>
> > Car history: Bought new in '98 and treated well. NO work of any
> > kind has been required under the hood.
>
> > He says it has not affected the performace of his Explorer and it
> > doesn't have any problems or run rough starting in cold weather. He
> > also left my Haynes repair manual at school. I think this is the OHV
> > version? Most if not all of the post refer to the SOHC model.
>
> > What should I start to do since he will be home for only a few
> > days? Any help would be appreciated.
>
> > /Richard
>
> Here's a place that describes your trouble codes:
>
> http://www.obd-codes.com/p0171- Hide quoted text -
>
> - Show quoted text -

Thank you,

I will start looking for vacume leaks and clean the MAF first.
Thanks again.

/Richard

Let's just hope it's as easy to fix as it sounds like :-)

On Tue, 5 May 2009 12:46:01 -0700, "Ulysses"
> wrote:

>
>"Richard" > wrote in message
...
>On May 4, 11:57 am, "Ulysses" > wrote:
>> "Richard" > wrote in message
>>
>> ...
>>
>>
>>
>>
>>
>> > My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
>> > has been showing P0171 and P0174 codes for the last several months.
>> > (just came home from college today) He has been getting them reset
>> > (cleared) and after several days they come back on.
>>
>> > Car history: Bought new in '98 and treated well. NO work of any
>> > kind has been required under the hood.
>>
>> > He says it has not affected the performace of his Explorer and it
>> > doesn't have any problems or run rough starting in cold weather. He
>> > also left my Haynes repair manual at school. I think this is the OHV
>> > version? Most if not all of the post refer to the SOHC model.
>>
>> > What should I start to do since he will be home for only a few
>> > days? Any help would be appreciated.
>>
>> > /Richard
>>
>> Here's a place that describes your trouble codes:
>>
>> http://www.obd-codes.com/p0171- Hide quoted text -
>>
>> - Show quoted text -
>
>Thank you,
>
> I will start looking for vacume leaks and clean the MAF first.
>Thanks again.
>
>/Richard
>
>Let's just hope it's as easy to fix as it sounds like :-)
>

O2 sensor codes are often bad sensors, at least in my experience.

"PeterD" > wrote in message
...
> On Tue, 5 May 2009 12:46:01 -0700, "Ulysses"
> > wrote:
>
> >
> >"Richard" > wrote in message
> ...
> >On May 4, 11:57 am, "Ulysses" > wrote:
> >> "Richard" > wrote in message
> >>
> >>
...
> >>
> >>
> >>
> >>
> >>
> >> > My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
> >> > has been showing P0171 and P0174 codes for the last several months.
> >> > (just came home from college today) He has been getting them reset
> >> > (cleared) and after several days they come back on.
> >>
> >> > Car history: Bought new in '98 and treated well. NO work of any
> >> > kind has been required under the hood.
> >>
> >> > He says it has not affected the performace of his Explorer and it
> >> > doesn't have any problems or run rough starting in cold weather. He
> >> > also left my Haynes repair manual at school. I think this is the OHV
> >> > version? Most if not all of the post refer to the SOHC model.
> >>
> >> > What should I start to do since he will be home for only a few
> >> > days? Any help would be appreciated.
> >>
> >> > /Richard
> >>
> >> Here's a place that describes your trouble codes:
> >>
> >> http://www.obd-codes.com/p0171- Hide quoted text -
> >>
> >> - Show quoted text -
> >
> >Thank you,
> >
> > I will start looking for vacume leaks and clean the MAF first.
> >Thanks again.
> >
> >/Richard
> >
> >Let's just hope it's as easy to fix as it sounds like :-)
> >
>
> O2 sensor codes are often bad sensors, at least in my experience.

I have a PO136 and a PO141 on my '97 (4.0L OHV) and my
brother-in-law-mechanic told me to check the voltage at the sensor. If the
voltage is good then the sensor is bad.

OTOH I've had a CEL come on (same vehicle) and it went off after I cleaned
the MAF, replaced the air filter, and cleaned the IAC (for good measure).
It didn't come back on but in that case I didn't have a code reader
available. Just dumb luck I guess.

Someday I would like to see a list of all the things that make the CEL come
on so guys like me can at least try a few things before spending a bunch of
money. Most of my Fords aren't worth paying someone to fix. It's kinda
scary cause there isn't much input in this NG any more so I can only hope my
luck continues.

On Wed, 6 May 2009 18:52:04 -0700, "Ulysses"
> wrote:

>
>"PeterD" > wrote in message
.. .
>> On Tue, 5 May 2009 12:46:01 -0700, "Ulysses"
>> > wrote:
>>
>> >
>> >"Richard" > wrote in message
>> ...
>> >On May 4, 11:57 am, "Ulysses" > wrote:
>> >> "Richard" > wrote in message
>> >>
>> >>
...
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> > My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
>> >> > has been showing P0171 and P0174 codes for the last several months.
>> >> > (just came home from college today) He has been getting them reset
>> >> > (cleared) and after several days they come back on.
>> >>
>> >> > Car history: Bought new in '98 and treated well. NO work of any
>> >> > kind has been required under the hood.
>> >>
>> >> > He says it has not affected the performace of his Explorer and it
>> >> > doesn't have any problems or run rough starting in cold weather. He
>> >> > also left my Haynes repair manual at school. I think this is the OHV
>> >> > version? Most if not all of the post refer to the SOHC model.
>> >>
>> >> > What should I start to do since he will be home for only a few
>> >> > days? Any help would be appreciated.
>> >>
>> >> > /Richard
>> >>
>> >> Here's a place that describes your trouble codes:
>> >>
>> >> http://www.obd-codes.com/p0171- Hide quoted text -
>> >>
>> >> - Show quoted text -
>> >
>> >Thank you,
>> >
>> > I will start looking for vacume leaks and clean the MAF first.
>> >Thanks again.
>> >
>> >/Richard
>> >
>> >Let's just hope it's as easy to fix as it sounds like :-)
>> >
>>
>> O2 sensor codes are often bad sensors, at least in my experience.
>
>I have a PO136 and a PO141 on my '97 (4.0L OHV) and my
>brother-in-law-mechanic told me to check the voltage at the sensor. If the
>voltage is good then the sensor is bad.

Some how the concept that the voltage being right at the sensor
dictates the sensor is bad is puzzling... <g>

>
>OTOH I've had a CEL come on (same vehicle) and it went off after I cleaned
>the MAF, replaced the air filter, and cleaned the IAC (for good measure).
>It didn't come back on but in that case I didn't have a code reader
>available. Just dumb luck I guess.

Could have been dumb luck, but what you did was sensible, and
reasonable.

>
>Someday I would like to see a list of all the things that make the CEL come
>on so guys like me can at least try a few things before spending a bunch of
>money. Most of my Fords aren't worth paying someone to fix. It's kinda
>scary cause there isn't much input in this NG any more so I can only hope my
>luck continues.
>

A scan tool is your friend. Personally I own my own scan tool (OK, I
have *five* of them...) but many parts stores will scan for 'free'.

Frequently I can clear the DTCs for a vehicle and they won't come back
on. This is always the best first start, certainly the cheapest one.
Sometimes it is a transient problem, and it never reoccures.

"PeterD" > wrote in message
...
> On Wed, 6 May 2009 18:52:04 -0700, "Ulysses"
> > wrote:
>
> >
> >"PeterD" > wrote in message
> .. .
> >> On Tue, 5 May 2009 12:46:01 -0700, "Ulysses"
> >> > wrote:
> >>
> >> >
> >> >"Richard" > wrote in message
> >>
...
> >> >On May 4, 11:57 am, "Ulysses" > wrote:
> >> >> "Richard" > wrote in message
> >> >>
> >> >>
> ...
> >> >>
> >> >>
> >> >>
> >> >>
> >> >>
> >> >> > My son's '99 XLS 4.0 (cheaper engine, I think) with 97K miles
> >> >> > has been showing P0171 and P0174 codes for the last several
months.
> >> >> > (just came home from college today) He has been getting them reset
> >> >> > (cleared) and after several days they come back on.
> >> >>
> >> >> > Car history: Bought new in '98 and treated well. NO work of any
> >> >> > kind has been required under the hood.
> >> >>
> >> >> > He says it has not affected the performace of his Explorer and it
> >> >> > doesn't have any problems or run rough starting in cold weather.
He
> >> >> > also left my Haynes repair manual at school. I think this is the
OHV
> >> >> > version? Most if not all of the post refer to the SOHC model.
> >> >>
> >> >> > What should I start to do since he will be home for only a few
> >> >> > days? Any help would be appreciated.
> >> >>
> >> >> > /Richard
> >> >>
> >> >> Here's a place that describes your trouble codes:
> >> >>
> >> >> http://www.obd-codes.com/p0171- Hide quoted text -
> >> >>
> >> >> - Show quoted text -
> >> >
> >> >Thank you,
> >> >
> >> > I will start looking for vacume leaks and clean the MAF first.
> >> >Thanks again.
> >> >
> >> >/Richard
> >> >
> >> >Let's just hope it's as easy to fix as it sounds like :-)
> >> >
> >>
> >> O2 sensor codes are often bad sensors, at least in my experience.
> >
> >I have a PO136 and a PO141 on my '97 (4.0L OHV) and my
> >brother-in-law-mechanic told me to check the voltage at the sensor. If
the
> >voltage is good then the sensor is bad.
>
> Some how the concept that the voltage being right at the sensor
> dictates the sensor is bad is puzzling... <g>

It seems clear to me ;-) What I meant was if you have a code indicating a
bad sensor and the wiring check out OK, and the proper voltage it getting TO
the sensor, then the sensor must be bad.

>
> >
> >OTOH I've had a CEL come on (same vehicle) and it went off after I
cleaned
> >the MAF, replaced the air filter, and cleaned the IAC (for good measure).
> >It didn't come back on but in that case I didn't have a code reader
> >available. Just dumb luck I guess.
>
> Could have been dumb luck, but what you did was sensible, and
> reasonable.
>
> >
> >Someday I would like to see a list of all the things that make the CEL
come
> >on so guys like me can at least try a few things before spending a bunch
of
> >money. Most of my Fords aren't worth paying someone to fix. It's kinda
> >scary cause there isn't much input in this NG any more so I can only hope
my
> >luck continues.
> >
>
> A scan tool is your friend. Personally I own my own scan tool (OK, I
> have *five* of them...) but many parts stores will scan for 'free'.

My local parts stores used to scan for free but now they say the government
won't let them do it any more. I guess the Auto Mechanics Union or somebody
paid off the govment.

>
> Frequently I can clear the DTCs for a vehicle and they won't come back
> on. This is always the best first start, certainly the cheapest one.
> Sometimes it is a transient problem, and it never reoccures.

I've had results getting the CEL to go off by disconnecting the battery for
a while but that was always when I did something like disconnect the
throttle position sensor which should make the CEL come on. Sooner or later
I'll have to get a code reader or start buying older cars ;-). Right now I
have a '99 Ranger with auto trans problems and unfortunately I think I've
eliminated all of the possible electronic and sensor problems so that leaves
me with needing a rebuild/replacement. If I had a bad speed sensor would it
show up as a trouble code? I have no codes and have had them read twice.

On Thu, 7 May 2009 08:11:16 -0700, "Ulysses"
> wrote:

>
>"PeterD" > wrote in message
.. .
>>
>> Some how the concept that the voltage being right at the sensor
>> dictates the sensor is bad is puzzling... <g>
>
>It seems clear to me ;-) What I meant was if you have a code indicating a
>bad sensor and the wiring check out OK, and the proper voltage it getting TO
>the sensor, then the sensor must be bad.

Perhaps misundertanding, but an O2 sensor generates voltage, and
doesn't 'get' voltage. So if the voltage at the O2 sensor is right,
then the sensor had to be good. <g>

>
>>
>> A scan tool is your friend. Personally I own my own scan tool (OK, I
>> have *five* of them...) but many parts stores will scan for 'free'.
>
>My local parts stores used to scan for free but now they say the government
>won't let them do it any more. I guess the Auto Mechanics Union or somebody
>paid off the govment.

You must be in one of those states where you have no freedom at all.
Like CA for example where you can't wipe your butt whtout running
afoul of the law! <bg> They (scan tools) are not expensive, a good
investment IMHO, especially if you live there!

>
>>
>> Frequently I can clear the DTCs for a vehicle and they won't come back
>> on. This is always the best first start, certainly the cheapest one.
>> Sometimes it is a transient problem, and it never reoccures.
>
>I've had results getting the CEL to go off by disconnecting the battery for
>a while but that was always when I did something like disconnect the
>throttle position sensor which should make the CEL come on. Sooner or later
>I'll have to get a code reader or start buying older cars ;-).

Really old cars! Like from the 60's. But wait, taht won't work because
some states are now forcing people to scrap these older, classic cars.
> Right now I
>have a '99 Ranger with auto trans problems and unfortunately I think I've
>eliminated all of the possible electronic and sensor problems so that leaves
>me with needing a rebuild/replacement. If I had a bad speed sensor would it
>show up as a trouble code? I have no codes and have had them read twice.
>

I guess more information about what's happening would be best. Is it a
4x4? IIRC, the sensor for speed is in the tcase, same connector as the
tcase shift motor.

"PeterD" > wrote in message
...
> On Thu, 7 May 2009 08:11:16 -0700, "Ulysses"
> > wrote:
>
> >
> >"PeterD" > wrote in message
> .. .
> >>
> >> Some how the concept that the voltage being right at the sensor
> >> dictates the sensor is bad is puzzling... <g>
> >
> >It seems clear to me ;-) What I meant was if you have a code indicating
a
> >bad sensor and the wiring check out OK, and the proper voltage it getting
TO
> >the sensor, then the sensor must be bad.
>
> Perhaps misundertanding, but an O2 sensor generates voltage, and
> doesn't 'get' voltage. So if the voltage at the O2 sensor is right,
> then the sensor had to be good. <g>
>
> >
> >>
> >> A scan tool is your friend. Personally I own my own scan tool (OK, I
> >> have *five* of them...) but many parts stores will scan for 'free'.
> >
> >My local parts stores used to scan for free but now they say the
government
> >won't let them do it any more. I guess the Auto Mechanics Union or
somebody
> >paid off the govment.
>
> You must be in one of those states where you have no freedom at all.
> Like CA for example where you can't wipe your butt whtout running
> afoul of the law! <bg> They (scan tools) are not expensive, a good
> investment IMHO, especially if you live there!
>
> >
> >>
> >> Frequently I can clear the DTCs for a vehicle and they won't come back
> >> on. This is always the best first start, certainly the cheapest one.
> >> Sometimes it is a transient problem, and it never reoccures.
> >
> >I've had results getting the CEL to go off by disconnecting the battery
for
> >a while but that was always when I did something like disconnect the
> >throttle position sensor which should make the CEL come on. Sooner or
later
> >I'll have to get a code reader or start buying older cars ;-).
>
> Really old cars! Like from the 60's. But wait, taht won't work because
> some states are now forcing people to scrap these older, classic cars.
> > Right now I
> >have a '99 Ranger with auto trans problems and unfortunately I think I've
> >eliminated all of the possible electronic and sensor problems so that
leaves
> >me with needing a rebuild/replacement. If I had a bad speed sensor would
it
> >show up as a trouble code? I have no codes and have had them read twice.
> >
>
> I guess more information about what's happening would be best. Is it a
> 4x4? IIRC, the sensor for speed is in the tcase, same connector as the
> tcase shift motor.