Re: P0171/P0174 Help!

Technical aspects of automobiles, et. al., post #21,712
Author:
Date:
Subject:
 W. Stief
 2008-07-19 21:46:17
 Re: P0171/P0174 Help!
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?


>
>
>
>
>
>> "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!
Author:
Date:
Subject:
 aarcuda69062
 2008-07-20 08:41:41
 Re: P0171/P0174 Help!
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?
Author:
Date:
Subject:
 Steve W.
 2008-07-20 10:53:45
 Re: P0171/P0174 Help!
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?

--
Steve W.
Author:
Date:
Subject:
 Pete C.
 2008-07-20 10:05:36
 Re: P0171/P0174 Help!
"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.
Author:
Date:
Subject:
 aarcuda69062
 2008-07-20 10:42:41
 Re: P0171/P0174 Help!
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.
Author:
Date:
Subject:
 Steve W.
 2008-07-20 11:59:06
 Re: P0171/P0174 Help!
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.

--
Steve W.
Author:
Date:
Subject:
 Pete C.
 2008-07-20 11:45:37
 Re: P0171/P0174 Help!
"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.