Re: P0171/P0174 Help! *update*

In article <dYafk.32612$ZE5.7110@nlpi061.nbdc.sbc.com>,
"Pete C." <[email protected]> wrote:

> "Pete C." wrote:
> >
> > '97 Chev K3500 7.4L
> >
> > Been chasing after the source of intermittent P0171/P0174 (always both
> > set) for some time without success. I'm running out of ideas on what to
> > check now, I don't have a full feature scan tool so I can't perform all
> > the possible checks. Some of the possible items seem to not be
> > applicable due to it always setting both codes, i.e. exhaust or HO2S
> > issues not likely since it's dual exhaust with dual cats.
> >
> > I've replaced the fuel pump recently and the tank interior was spotless,
> > so clogging / contamination is not likely. I just replaced the FPR and
> > it's filter screen was clean as well. The FPR did fix pressure leak down
> > on pump shutoff, but that seems to not have been a significant issue.
> >
> > I did plugs/wires/cap/rotor while I was at it this last service
> > Saturday, and the removed plugs all had moderate tan deposits that seem
> > consistent with the 130k or so on them. I also cleaned the IM passages
> > and ports while things were apart.
> >
> > I do have freeze frame data from the trouble codes as noted below:
> >
> > Closed loop / closed loop
> > Calc. load 19.2%
> > Coolant temp 167F
> > ST1 0.7%
> > LT1 24.9%
> > ST2 1.5%
> > LT2 24.9%
> > MAP 17.4 in/hg
> > RPM 2521
> > MPH 65
> > MAF 7.152 lb/min
> > TPS 20.7%
> >
> > No trouble codes other than the P0171/P0174 have ever been set.
> >
> > Any ideas where else to look?
> >
> > Thanks!
>
> After erasing the previous codes and logging another 140 miles or so, I
> have yet another set of P0171/P0174 set and another pending set. New
> freeze data is as follows:
>
> Closed loop / closed loop
> Calc. load 10.1%
> Coolant temp 172F
> ST1 17.9%
> LT1 24.9%
> ST2 21.0%
> LT2 24.9%
> MAP 17.1 in/hg
> RPM 1489
> MPH 28
> MAF 3.875 lb/min
> TPS 12.9%

What is the fuel pressure during these conditions (simulate the freeze
frame)?

Can you get the MAF reading at whatever is the safest maximum RPM for
that engine at WOT?

Does your scan tool support graphing?

aarcuda69062 wrote:
>
> In article <dYafk.32612$ZE5.7110@nlpi061.nbdc.sbc.com>,
> "Pete C." <[email protected]> wrote:
>
> > "Pete C." wrote:
> > >
> > > '97 Chev K3500 7.4L
> > >
> > > Been chasing after the source of intermittent P0171/P0174 (always both
> > > set) for some time without success. I'm running out of ideas on what to
> > > check now, I don't have a full feature scan tool so I can't perform all
> > > the possible checks. Some of the possible items seem to not be
> > > applicable due to it always setting both codes, i.e. exhaust or HO2S
> > > issues not likely since it's dual exhaust with dual cats.
> > >
> > > I've replaced the fuel pump recently and the tank interior was spotless,
> > > so clogging / contamination is not likely. I just replaced the FPR and
> > > it's filter screen was clean as well. The FPR did fix pressure leak down
> > > on pump shutoff, but that seems to not have been a significant issue.
> > >
> > > I did plugs/wires/cap/rotor while I was at it this last service
> > > Saturday, and the removed plugs all had moderate tan deposits that seem
> > > consistent with the 130k or so on them. I also cleaned the IM passages
> > > and ports while things were apart.
> > >
> > > I do have freeze frame data from the trouble codes as noted below:
> > >
> > > Closed loop / closed loop
> > > Calc. load 19.2%
> > > Coolant temp 167F
> > > ST1 0.7%
> > > LT1 24.9%
> > > ST2 1.5%
> > > LT2 24.9%
> > > MAP 17.4 in/hg
> > > RPM 2521
> > > MPH 65
> > > MAF 7.152 lb/min
> > > TPS 20.7%
> > >
> > > No trouble codes other than the P0171/P0174 have ever been set.
> > >
> > > Any ideas where else to look?
> > >
> > > Thanks!
> >
> > After erasing the previous codes and logging another 140 miles or so, I
> > have yet another set of P0171/P0174 set and another pending set. New
> > freeze data is as follows:
> >
> > Closed loop / closed loop
> > Calc. load 10.1%
> > Coolant temp 172F
> > ST1 17.9%
> > LT1 24.9%
> > ST2 21.0%
> > LT2 24.9%
> > MAP 17.1 in/hg
> > RPM 1489
> > MPH 28
> > MAF 3.875 lb/min
> > TPS 12.9%
>
> What is the fuel pressure during these conditions (simulate the freeze
> frame)?
>
> Can you get the MAF reading at whatever is the safest maximum RPM for
> that engine at WOT?
>
> Does your scan tool support graphing?

Not sure I have a way to simulate a load. I also don't have a "real"
scan tool to read parameters in real time. All I have is the "good"
Harbor Freight CAN / OBD2 scanner that displays / clears codes and
displays associated freeze data. I do have a friend with a real scanner
(Snap-On I believe), so perhaps I can get a test plan together and visit
him.