Re: P0171/P0174 Help! *update*

In article <wEdfk.16479$89.6181@nlpi069.nbdc.sbc.com>,
"Pete C." <[email protected]> wrote:

> > Don't need to. Test drive it like you stole it, set the Snap-On scanner
> > in 'movie' mode, floor it in first gear and when it shifts to second,
>
> Woa there, "when it shifts to second"??? What do you think I am, some
> kinda wuss? I only drive trucks with real transmissions :) (NP4500 in
> this case). Heck, one of the reason I keep getting bigger trucks is my
> hatred of automatics.

Okay, when YOU shift to second.

> > hit the trigger on the scanner, review the movie near frame "0" forward
> > and backwards frame by frame until you find the max RPM, then scroll to
> > the MAF sensor and read the grams per second. With RPM, engine size and
> > a few other ambient details, I can calculate whether the theoretical
> > volumetric efficiency matches what the PCM PID are reporting.
> > I'm leaning towards three things; either the MAF sensor isn't reading
> > correctly or you have plugged injectors or your fuel pump can't keep up.
>
> Well, it's on the third or is it fourth fuel pump. Since the problem has
> existed over at least two pumps I'm inclined to think it's probably not
> the pump.

Doesn't mean it's not fuel pump related.
These things are well known for overheated harnesses in the tank and
where the FP module plugs in.

> The fuel injectors were replaced some 130k ago or so, at the same time
> the cats were replaced under warranty (also replaced all four HO2S). The
> facts that I always get both 171 and 174, all the recently pulled plugs
> were consistent, and the tank and FPR screens were all spotless leans me
> away from a fuel injector problem.

Still doesn't lean me away from an injector problem.
The PCM is still able to compensate for the lean condition, that's what
the fuel trim numbers indicate, so it's not unusual that the plug color
looks okay.

> The MAF, well, that's original, now with 199,500+ miles of use on it. I
> did clean it with CRC MAF cleaner, though there was no sign of any
> visible dirt on it.

Two ways to tell if it's functioning properly, take the measurements and
do the calculations or replace it with a new (not different) one.

> >
> > 44-45 percent fuel correction is HUGE, there is a real problem there and
> > you'd best fix it before there's collateral damage.
>
> I've certainly been trying to locate and fix it.
>
> >
> > > 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.
> >
> > That's not a scan tool. In my business, that's an invitation to
> > frustration.
>
> It's a step above a basic code reader at least. I may need to invest in
> something better, perhaps PC based, got any suggestions for something
> good, but less $$$ than pro stuff?

Autoenginuity.
http://www.autoenginuity.com/
You can get into the enhanced GM package for about $400

The interface sucks but isn't as bad as some, It graphs, does mode 6
conversion without any hexdecimal conversions, does cam offset relearn,
has bi-directional control, it is as close to a Tech 2 as you can get
without spending $6K. On a laptop platform, it's not as easy to
manipulate while driving as a dedicated scan tool.
Or, buy a Snap-On scanner off of e-bay, they're pretty low on resale.
http://motors.shop.ebay.com/_Automotive-Tools__W0QQToolType5b20e8c2ZDiagn
osticToolsEquipmentc18aef6QQ_catZ43989QQ_flnZ1QQ_pcatsZ34998Q2c6028Q2c600
0QQ_ssovZ1?_rkw=mt%202500