Re: P0171/P0174 Help!

Technical aspects of automobiles, et. al., post #21,742
Author:
Date:
Subject:
 Steve W.
 2008-07-20 13:38:34
 Re: P0171/P0174 Help!
Pete C. wrote:
> "Steve W." wrote:
>> aarcuda69062 wrote:
>>> In article <4vIgk.15801$mh5.4782@nlpi067.nbdc.sbc.com>,
>>> "Pete C." <[email protected]> wrote:
>>>
>>>> "Steve W." wrote:
>>>>> aarcuda69062 wrote:
>>>>>> In article <1Gxgk.33463$ZE5.8416@nlpi061.nbdc.sbc.com>,
>>>>>> "W. Stief" <[email protected]> wrote:
>>>>>>
>>>>>>>> Well, I sprayed some B12 around the IM while the engine was idling and
>>>>>>>> didn't note any detectable RPM change. The intake is stock and there
>>>>>>>> is a "normal" filter in place. I did try a K&N filter way back when
>>>>>>>> before deciding it was of no value. That was a long time ago and the
>>>>>>>> MAF has been cleaned with CRC MAF cleaner since then. Another freeze
>>>>>>>> frame had RPM at 2521 and MAF at 7.152 lb/min.
>>>>>>> How are your brakes working?
>>>>>> Why would his brakes cause a 2 lean trouble codes?
>>>>> Vacuum leak through the booster?
>>>> 1T dually - Hydroboost.
>>> The devil is in the details.
>> True, Scratch the booster leak.
>
> Not really much for vacuum lines on this truck, since it has hydroboost
> and they long since stopped using vacuum actuators for stuff like HVAC.
>
> I did find another issue when farting around with it yesterday. While
> the engine was idling I pulled the fuel pump relay and to my surprise
> watched the fuel pressure slowly drop until the engine died. Seems that
> the fuel pump oil pressure switch isn't doing it's thing. The oil
> pressure gauge reads normally and it's a combined switch / sensor unit,
> so presumably the oil pressure is fine. There doesn't seem to be an easy
> way to connect a direct pressure gauge to validate. I need to connect a
> meter to the wiring near the fuel pump and see if it's suffering a
> voltage drop under load due to perhaps burned relay contacts.
>
> I also disco'd the fuel filter and checked it yesterday. The fuel filter
> flowed freely, so it was reinstalled when I was done (did have another
> filter on hand). While it was out I connected a hose to the supply side
> line and ran it into a gas can. I put my manual switch in place of the
> fuel pump relay and powered it up and it seemed to pump more than enough
> volume.

OK you said you had access to a Snap-On scanner. Do you have access to a
scope? If yes connect up to the fuel pumps power and make sure your not
losing any voltage or amperage through the line. Either one could cause
the pump to slow enough that it could be starving the engine.

I'll trade you problems. I have a 96 Jeep in the shop. with a NO run
problem. Connected the scanner and it can't connect to the PCM. Checked
for proper power and grounds and they are good. Stuck a new PCM in and
still no joy. Started looking deeper and so far the only common thing is
that the PCM isn't working and there seems to be no reason for it.
Jumped around any switches or relays and still nothing. So now I'm going
through the harness looking for a problem.. It's only 106 wires though....

--
Steve W.
Author:
Date:
Subject:
 Pete C.
 2008-07-20 14:04:31
 Re: P0171/P0174 Help!
"Steve W." wrote:
>
> Pete C. wrote:
> > "Steve W." wrote:
> >> aarcuda69062 wrote:
> >>> In article <4vIgk.15801$mh5.4782@nlpi067.nbdc.sbc.com>,
> >>> "Pete C." <[email protected]> wrote:
> >>>
> >>>> "Steve W." wrote:
> >>>>> aarcuda69062 wrote:
> >>>>>> In article <1Gxgk.33463$ZE5.8416@nlpi061.nbdc.sbc.com>,
> >>>>>> "W. Stief" <[email protected]> wrote:
> >>>>>>
> >>>>>>>> Well, I sprayed some B12 around the IM while the engine was idling and
> >>>>>>>> didn't note any detectable RPM change. The intake is stock and there
> >>>>>>>> is a "normal" filter in place. I did try a K&N filter way back when
> >>>>>>>> before deciding it was of no value. That was a long time ago and the
> >>>>>>>> MAF has been cleaned with CRC MAF cleaner since then. Another freeze
> >>>>>>>> frame had RPM at 2521 and MAF at 7.152 lb/min.
> >>>>>>> How are your brakes working?
> >>>>>> Why would his brakes cause a 2 lean trouble codes?
> >>>>> Vacuum leak through the booster?
> >>>> 1T dually - Hydroboost.
> >>> The devil is in the details.
> >> True, Scratch the booster leak.
> >
> > Not really much for vacuum lines on this truck, since it has hydroboost
> > and they long since stopped using vacuum actuators for stuff like HVAC.
> >
> > I did find another issue when farting around with it yesterday. While
> > the engine was idling I pulled the fuel pump relay and to my surprise
> > watched the fuel pressure slowly drop until the engine died. Seems that
> > the fuel pump oil pressure switch isn't doing it's thing. The oil
> > pressure gauge reads normally and it's a combined switch / sensor unit,
> > so presumably the oil pressure is fine. There doesn't seem to be an easy
> > way to connect a direct pressure gauge to validate. I need to connect a
> > meter to the wiring near the fuel pump and see if it's suffering a
> > voltage drop under load due to perhaps burned relay contacts.
> >
> > I also disco'd the fuel filter and checked it yesterday. The fuel filter
> > flowed freely, so it was reinstalled when I was done (did have another
> > filter on hand). While it was out I connected a hose to the supply side
> > line and ran it into a gas can. I put my manual switch in place of the
> > fuel pump relay and powered it up and it seemed to pump more than enough
> > volume.
>
> OK you said you had access to a Snap-On scanner. Do you have access to a
> scope? If yes connect up to the fuel pumps power and make sure your not
> losing any voltage or amperage through the line. Either one could cause
> the pump to slow enough that it could be starving the engine.

The Snap-On scanner is one of the fancy graphing, scopeing, coffee
making ones :) I don't need it for those checks though, I can do those
with my Fluke 87.

>
> I'll trade you problems. I have a 96 Jeep in the shop. with a NO run
> problem. Connected the scanner and it can't connect to the PCM. Checked
> for proper power and grounds and they are good. Stuck a new PCM in and
> still no joy. Started looking deeper and so far the only common thing is
> that the PCM isn't working and there seems to be no reason for it.
> Jumped around any switches or relays and still nothing. So now I'm going
> through the harness looking for a problem.. It's only 106 wires though....

Connectors, it's always the connectors, especially in a harsh auto
environment... well, at least it is when it isn't a mouse eaten wire :(
Author:
Date:
Subject:
 Pete C.
 2008-07-20 15:14:02
 Re: P0171/P0174 Help!
"Pete C." wrote:
>
> "Steve W." wrote:
> >
> > Pete C. wrote:
> > > "Steve W." wrote:
> > >> aarcuda69062 wrote:
> > >>> In article <4vIgk.15801$mh5.4782@nlpi067.nbdc.sbc.com>,
> > >>> "Pete C." <[email protected]> wrote:
> > >>>
> > >>>> "Steve W." wrote:
> > >>>>> aarcuda69062 wrote:
> > >>>>>> In article <1Gxgk.33463$ZE5.8416@nlpi061.nbdc.sbc.com>,
> > >>>>>> "W. Stief" <[email protected]> wrote:
> > >>>>>>
> > >>>>>>>> Well, I sprayed some B12 around the IM while the engine was idling and
> > >>>>>>>> didn't note any detectable RPM change. The intake is stock and there
> > >>>>>>>> is a "normal" filter in place. I did try a K&N filter way back when
> > >>>>>>>> before deciding it was of no value. That was a long time ago and the
> > >>>>>>>> MAF has been cleaned with CRC MAF cleaner since then. Another freeze
> > >>>>>>>> frame had RPM at 2521 and MAF at 7.152 lb/min.
> > >>>>>>> How are your brakes working?
> > >>>>>> Why would his brakes cause a 2 lean trouble codes?
> > >>>>> Vacuum leak through the booster?
> > >>>> 1T dually - Hydroboost.
> > >>> The devil is in the details.
> > >> True, Scratch the booster leak.
> > >
> > > Not really much for vacuum lines on this truck, since it has hydroboost
> > > and they long since stopped using vacuum actuators for stuff like HVAC.
> > >
> > > I did find another issue when farting around with it yesterday. While
> > > the engine was idling I pulled the fuel pump relay and to my surprise
> > > watched the fuel pressure slowly drop until the engine died. Seems that
> > > the fuel pump oil pressure switch isn't doing it's thing. The oil
> > > pressure gauge reads normally and it's a combined switch / sensor unit,
> > > so presumably the oil pressure is fine. There doesn't seem to be an easy
> > > way to connect a direct pressure gauge to validate. I need to connect a
> > > meter to the wiring near the fuel pump and see if it's suffering a
> > > voltage drop under load due to perhaps burned relay contacts.
> > >
> > > I also disco'd the fuel filter and checked it yesterday. The fuel filter
> > > flowed freely, so it was reinstalled when I was done (did have another
> > > filter on hand). While it was out I connected a hose to the supply side
> > > line and ran it into a gas can. I put my manual switch in place of the
> > > fuel pump relay and powered it up and it seemed to pump more than enough
> > > volume.
> >
> > OK you said you had access to a Snap-On scanner. Do you have access to a
> > scope? If yes connect up to the fuel pumps power and make sure your not
> > losing any voltage or amperage through the line. Either one could cause
> > the pump to slow enough that it could be starving the engine.
>
> The Snap-On scanner is one of the fancy graphing, scopeing, coffee
> making ones :) I don't need it for those checks though, I can do those
> with my Fluke 87.
>
> >
> > I'll trade you problems. I have a 96 Jeep in the shop. with a NO run
> > problem. Connected the scanner and it can't connect to the PCM. Checked
> > for proper power and grounds and they are good. Stuck a new PCM in and
> > still no joy. Started looking deeper and so far the only common thing is
> > that the PCM isn't working and there seems to be no reason for it.
> > Jumped around any switches or relays and still nothing. So now I'm going
> > through the harness looking for a problem.. It's only 106 wires though....
>
> Connectors, it's always the connectors, especially in a harsh auto
> environment... well, at least it is when it isn't a mouse eaten wire :(

I get 12.7V at the fuel pump connector by the tank vs. 13.8V at the
battery terminals. I cleaned and tightened down the fuel pump ground
terminal while I was at it, but it was plenty solid to begin with. I
also popped the cover on the fuel pump relay and the contact look
perfect.
Author:
Date:
Subject:
 Pete C.
 2008-07-20 10:05:06
 Re: P0171/P0174 Help!
"W. Stief" wrote:
>
> Pete C. wrote:
> > mr158912 wrote:
> >>
> >> it seems to me you have a vacumm leak of some sort either intake
> >> plenium/manifold gsaket or egr valve and maybe evan a pcv system
> >> leak
> >> but looking at your posted data even without o2 data i must ask if
> >> you have a cold air intake kit with a k&n filter the oil from them
> >> plays hell with the maf sensors
> >> i would expect to see a little more maf signal at 1400rpms
> >> mike the days of your kind of repairs and troubleshooting are going
> >> away fast
> >
> > Well, I sprayed some B12 around the IM while the engine was idling and
> > didn't note any detectable RPM change. The intake is stock and there
> > is a "normal" filter in place. I did try a K&N filter way back when
> > before deciding it was of no value. That was a long time ago and the
> > MAF has been cleaned with CRC MAF cleaner since then. Another freeze
> > frame had RPM at 2521 and MAF at 7.152 lb/min.
>
> How are your brakes working?

Seemingly just fine. They are due for service when I find a free weekend
(really when I have the ambition to press out studs), but no indication
of sticking. Last time I put the jack under the truck and tried turning
the wheels by hand there was no apparent drag, which is what I presume
you're getting at. I'll check again when I get a chance a bit later
today.