P0174

[Doubeleive]

just ticked over 203k on this trip, will be at 203.5 by the time i’m back home

do you have a scanner that can read the maf data?, it might be worth doing a drive record and see what the maf data shows.
from my own personal experience the maf's on the gmt800's can start going goofy around 160k miles, after that they are questionable in my book, had more than a couple go bad before. not saying go drop more money on one but I would at least see what it is showing data wise. also check what the fuel trims are

 

[Doubeleive]

Definitely can be a dead or intermittently sticking injector. Injector balance test is best tool to diagnose that. Maybe pull the plugs on that bank to inspect them?

On the O2 sensors, you could swap the left and right (upstream only) to see if it's the one mis-reporting, if you don't mind crawling underneath and getting a bit dirty. And see if the problem switches with the other bank. Kinda of a pain, but that only costs some of your time. Just make sure truck is warm, not hot.

yep that's another thing to try

 

[hmclaughlin67]

do you have a scanner that can read the maf data?, it might be worth doing a drive record and see what the maf data shows.
from my own personal experience the maf's on the gmt800's can start going goofy around 160k miles, after that they are questionable in my book, had more than a couple go bad before. not saying go drop more money on one but I would at least see what it is showing data wise. also check what the fuel trims are

sits around 1.2lb/min at idle while warm

 

[Fless]

sits around 1.2lb/min at idle while warm

It would be easier for everyone if you have it display in g/s. 1.2lb/min = just over 9 g/s if my conversion is right; that's a lot for your 5.3. Should be around 5.3 g/s at idle, about equal to the displacement in liters.

Also, to clean injectors, if it's a Flex Fuel engine you could run some E85 in it if that's available in your area.

 

[Doubeleive]

@swathdiver @Fless does that seem low? Or high lol

 

[Fless]

9 g/s seems high. At idle it should be closer to the displacement in liters.

EDIT: https://www.motorverso.com/what-should-maf-read-at-idle/

 

[strutaeng]

Yeah, 9 gr/sec definitely seems too high to me as well.

Now, I thought underreporting caused lean conditions and overreporting caused rich conditions. Is that correct? Or I got that reversed?

Seems the opposite of OP's situation?

 

[Doubeleive]

Yeah, 9 gr/sec definitely seems too high to me as well.

Now, I thought underreporting caused lean conditions and overreporting caused rich conditions. Is that correct? Or I got that reversed?

Seems the opposite of OP's situation?

that's what i thought but I don't know a lot about the maf other than the mf's can cause a headache, I have had them cause all kinds of codes, misfire, lean, bad cat, throttle body, vacum leak, shifting problems, you name it.

 

[Marky Dissod]

LEAN means pcm / ecm sees too much O2. Correction is to add more fuel.
RICH means pcm / ecm sees too much HC. Correction is to subtract fuel.

In other words, if it's running rich, it THINKS it was running lean before it applied corrections.
It's @ 9 grams / sec because that what it takes to make the pre-cat O2 sensors happy.

MAF sensor is not the boss. It just says how much air flows past it. It can easily be fooled / tricked / misguided / just plain wrong.
Pre-cat O2 sensors are the boss. If they see lean, fuel will get added. If they see rich, fuel will get subtracted.

Check for vacuum leakage / gaps between MAF sensor and pre-cat O2 sensors (besides the hole you just taped shut).

 

[strutaeng]

that's what i thought but I don't know a lot about the maf other than the mf's can cause a headache, I have had them cause all kinds of codes, misfire, lean, bad cat, throttle body, vacum leak, shifting problems, you name it.

Ok, looks like we're correct:

https://www.motortrend.com/how-to/1402-understanding-maf-sensors-technically-speaking/

I believe I mentioned that an issue with the MAF would cause both banks to be lean or rich, which is not the OP's case. But definitely MAF values seem out of range and need to be investigated further...

And the rule that there could be more than one problem always seems to apply on these types of issues. I guess try to solve the problem by taking it step by step, fixing known problems first.