H3 Hummer H3 2006 - error code P0171 (poor mix) and excessive consumption

[Jorge]

Hi, I have a Hummer H3 2006 vortex 3.5 lts engine with the following faults:

- Check the check with error code P0171 (poor mix) and
- Exaggerated fuel consumption

Generally speaking the van works perfectly. It does not show obvious faults in the operation except for an exaggerated consumption of fuel and the check light (P0171)

- The competition air filter system (open without cover) was replaced by the original
- Search for vacuum leaks (with a smoke machine). No leaks found
- The oxygen sensor (sensor 1) was replaced by an original ACDELCO
- The two catalysts were replaced (they had emptied it)
- The spark plugs were replaced by the original ACDELCO (they had others)
- Compression of the cylinders was measured (going from 180 to 195 psi) - According to the manual the maximum compression is 215 Psi
- The possibility of low fuel pressure is ruled out since its idling operation is normal (small intermittent variations due to poor fuel quality)
- Replacement of the flowmeter (MAF) with an original one (GM)
- On several occasions place Clean injectors in the fuel tank, however it does not show symptoms of dirty injectors

After doing all the above mentioned the problem (P0171 and excessive fuel consumption) follows the difference that after changing the MAF sensor the code P0171 became intermittent. That is: every two days approx The check light turns off and then turns on again
The most striking thing is that when scanning when the check light is OFF, this code is kept in "CURRENT CODES" and disappears in "PENDING CODES"
And when scanning when the check light is ON, that code is kept on both (CURRENT and PENDING CODES)

This van was referred to several specialists and can not find fault

Any suggestion. From already thank you very much

*Apologize for my bad english

 

[alrock]

Could the symptoms come from a weak fuel pump or clogged filter? It might be getting enough fuel at idle but once you step on the accelerator it cannot deliver enough fuel. You mention poor fuel quality, so maybe you have a clogged filter. It's part of the fuel pump assembly inside the tank.

 

[Jorge]

Could the symptoms come from a weak fuel pump or clogged filter? It might be getting enough fuel at idle but once you step on the accelerator it cannot deliver enough fuel. You mention poor fuel quality, so maybe you have a clogged filter. It's part of the fuel pump assembly inside the tank.

Thank you very much for the information. I'll keep it in mind

 

[RamRod]

What about the injectors, are they leaking?

 

[Happy Hummer]

Hey all!

To tired to type all of this stuff so here goes....(props to Doc Olds)....for info....

There could be a vacuum leak downstream of the MAF sensor, a possible cracked vacuum or PCV line/connection;

The MAF Sensor is dirty or faulty,
[The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.];

Failed or faulty oxygen sensor (bank 1 since I5s only have one, sensor 1=upstream);

Sticking/plugged or failed fuel injector;
Low fuel pressure (pump going bad);and,
Exhaust[FONT=verdana, geneva, lucida, lucida grande, arial, helvetica, sans-serif] leak between [/FONT]engine[FONT=verdana, geneva, lucida, lucida grande, arial, helvetica, sans-serif] and the upstream oxygen sensor[/FONT] (I5s are known to break exhaust manifold bolts)."

Notice the bold print last item? [FONT=verdana, geneva, lucida, lucida grande, arial, helvetica, sans-serif]

[/FONT]

That crack is likely a cause for the CEL, but it doesn't explain why you said the truck runs poorly at RPM.

[FONT=verdana, geneva, lucida, lucida grande, arial, helvetica, sans-serif]Cast manifolds can be welded, but the larger the crack the more difficult. Since full fusion penetration in welding thick cast material is not going to occur (it could be done through a certain process but this is not a welding metals forum and I am not going there), the downside is any weld will likely fail over time, especially with the vibrations the I5 puts out. [/FONT]


[FONT=verdana, geneva, lucida, lucida grande, arial, helvetica, sans-serif]By the way check your hose under the intake resonator box and make sure it is not dry rotted.[/FONT]


[FONT=verdana, geneva, lucida, lucida grande, arial, helvetica, sans-serif]chris[/FONT]

 

[Jorge]

thanks for the info

 

[CaseyS]

Where are you located? Possibly high ethanol content in the fuel lowering the heat content?

 

[powerlifter]

A couple of odd problems I had with a 171 were a rusted vacum line to the purge solenoid, and the top of the fuel pump was rusted, with pin holes. The vacuum line was rusted where it goes over top of the fuel tank, so it was not easy to see. Both of those problems created vacuum leaks that showed up as a code 0171