Lean both banks w/ no apparent air leaks

[ross reynolds]

Let me start by apologizing for asking about a Silverado, but I am stuck.
2007.5 Silverado LTZ Crew Cab 5.3 NNBS (GMT900) Lean both banks, no external air leaks found and averaging 25% fuel trim on each bank.


I’m Ross and I’m a parts changer. (Hi Ross!!!) I’m ashamed for not figuring this out but I’m stuck really needing some help. This started about 6 months after a black bear tune and AFM delete. I love the tune and realize this not the problem, but nonetheless spent several weeks trying to teach myself how to diagnose fuel trims, tried several things like cleaning MAF and throttle body, spraying starter fluid around joints to look for leaks, etc. . Next I found a local reputable shop and let them spend two weeks smoking the intake system multiple times while trying to figure it out, (and me renting a truck) they changed a couple of exhaust o2 sensors, and gave it back to me, not fixed. I spent more at another spot that couldn’t figure it out either. I try to not be an idiot, these were both shops with great diagnostic reviews, I have not gone to the dealer for this but only because I can’t afford for them to lie to me too.

This leads me to deciding, well I love the truck, it’s paid off, it runs like a top, clean, no visible smoke, no leaks, I’ll start methodically going through each system if I have to and replace things that I have learned are usually the problem in order. I can do it myself, I’m a contractor and a struggling family man with no dough, so my daily driver needs to be ready if I need anything. Next, the part replacement started and now that I have replaced (and correctly torqued in pattern when necessary) everything, the numbers are slightly better, but still ridiculous, setting lean codes and I’m sure it’s tripping the brake/traction control system as well.

No other problems, no misfires known of, etc. . Now I bought the truck with 100k, started a mobile1 synthetic oil regimen, have changed all serviceable fluids, blah blah blah. I’m going to attach a list of most things that I have done/changed. Everything I have bought has been stock, mainly ACdelco. Some of these things were not for lean issue but I try to keep a list so I can remember what and when I changed something. I’ve decided the problem must be internal but I have the AFM deleted so it shouldn’t be lifters right?

Well here’s the list, please help.


Silverado parts replaced


97,***

A. Bought truck, started 5k oil changes with Mobil1 full synthetic

150,***

A. Front wheel hubs, suspension joints and brake switch attached to

pedal arm.

B. Fluids (tranny 4 qt pumped from top, coolant, rear end, brake fluid,

and power steering.

C. Reengineered Dorman valve cover due to excessive oil

consumption

D. Kenwood touchscreen head unit with Nav, HD radio, Apple CarPlay,

Android, full Bluetooth with OEM steering wheel functionality, rear

seat controls and OnStar still working like new.

E. Dash cam (matched Kenwood) for fighting traffic tickets and

dumb-ass drivers.

F. Rear view full capability camera (matched Kenwood) mounted

inside square steel tube located directly above receiver tube for

trailer hitch. (Makes hooking up trailers by yourself easier than

EVER!)

G. Sport tune by Black Bear (California) w/ AFM delete

165,***

A. Fuel pump

B. Carbon filter

C. Vapor canister solenoid

D. Throttle body

E. Fuel cap

F. MAP sensor

G. MAF sensor

H. Master cylinder

I. Injectors professionally bench cleaned

J. Pre and post cat o2 sensors

K. AGM battery

L. Serpentine belt and tensioner pulley

M. PCV hose

N. Intake manifold gasket

185,***

A. Professional through fuel rail carbon clean

B. Power brake vacuum booster

C. Fuel vapor purge valve

D. Active brake control sensor

E. Big alternator (I think it’s the 160 amp)

F. Active brake control valve (pump) assembly and module

193,***

A. Intake manifold


My fuel pressure is 60psi, I’m running about 23% lean on each bank at idle and about 28% on each at 2500 rpm. This is a gas truck not flex fuel.

 

[Fless]

I assume that the 60psi fuel pressure was KOEO. What does the fuel pressure look like at the fuel rail as you're driving? Can you hook up a gauge and run the hose through the gap at the cowl and monitor it temporarily while you drive?

It's probably setting a code or two; what is it and can you look at freeze frame data for the snapshot?

 

[wsteele]

I agree, any codes?

Your truck can report fuel pressures as you drive by using the right scan tool (along with all the other sensor data).

 

[Fless]

It would be interesting to see a comparison of the fuel pressure that the system reports vs. what the gauge indicates, although I don't know if one can look at fuel rail pressure electronically (apples to apples).

EDIT: based on the high lean values at both RPMs I wouldn't think that a vacuum leak is indicated. I'd "lean" toward a fuel delivery issue. Pun intended.

EDIT again: has either the Fuel Pump Drive Module or the Fuel Injection Pressure Sensor been tested or changed?

 

[wsteele]

It would be interesting to see a comparison of the fuel pressure that the system reports vs. what the gauge indicates, although I don't know if one can look at fuel rail pressure electronically (apples to apples).

EDIT: based on the high lean values at both RPMs I wouldn't think that a vacuum leak is indicated. I'd "lean" toward a fuel delivery issue. Pun intended.

On his, for sure with a Tech 2, he can see realtime the fuel pressures, FP trims, etc. I would be surprised if my ODB dongle/iPhone scanner couldn't see his real time pressures.

It takes a pretty long hose to get the analog gauge to the wind screen. I will be able to say how long in about a week.

 

[Fless]

I'm just curious if the electronically reported fuel pressure is real....

 

[wsteele]

I'm just curious if the electronically reported fuel pressure is real....

Given how consistent the values seem to be when I have seen them on James, Ken and Tom’s when viewing their FPCM results on this system, I just assumed the sensor setup was pretty accurate.

 

[wsteele]

I'm just curious if the electronically reported fuel pressure is real....

Once again, if the OP has access to a Tech 2, all our questions might be answered.

 

[Doubeleive]

I would record a log file and send it blackbear for one and I would monitor your fuel pressure as far as I know 60psi should only be pre-start and should hang around 45-50 while driving. just my 2-cents of keyboard mechanic. you can get a fuel pressure gauge off of amazon or at harbor freight for $25-30, connect it and stick it up thru the gap in the hood hinge/wiper area so you can see it while driving. and don't worry about it being a silverado it's the same engine as the rest of the gm gang.

 

[FrankU]

Question , is this a Flex-Fuel engine ?