Re: P0171/P0174 Help!

Technical aspects of automobiles, et. al., post #21,750
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.
Author:
Date:
Subject:
 Steve Austin
 2008-07-20 13:57:05
 Re: P0171/P0174 Help!
Pete C. 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.
>
>
>
I'm coming in a little late here, so someone might have already
mentioned this. Pull the pcv hose off and the breather hose off the
valve cover and see if the engine is pulling a vacuum in the crankcase.
Sometimes the intake gaskets fail internally and suck from inside the
engine.
Author:
Date:
Subject:
 Pete C.
 2008-07-20 14:12:52
 Re: P0171/P0174 Help!
Steve Austin wrote:
>
> Pete C. 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.
> >
> >
> >
> I'm coming in a little late here, so someone might have already
> mentioned this. Pull the pcv hose off and the breather hose off the
> valve cover and see if the engine is pulling a vacuum in the crankcase.
> Sometimes the intake gaskets fail internally and suck from inside the
> engine.

Good vacuum at the end of the PCV valve when it's pulled out, no vacuum
(or pressure) detectable from the ports in the valve covers.