Re: P0171/P0174 Help!

Technical aspects of automobiles, et. al., post #21,700
Author:
Date:
Subject:
 mr158912
 2008-07-19 17:16:40
 Re: P0171/P0174 Help!
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
"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:
 Pete C.
 2008-07-19 19:40:32
 Re: P0171/P0174 Help!
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.





> "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:
 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.