P0101 and LT fuel trim high on both banks

I get a P0101 (MAF Sensor "A" Circuit Range/Performance) and I suspect the code is because the LT fuel trim on both banks is high, high teens, low 20s (%). The ST is around 0, plus or minus a few points.

Since it happens consistently across both engine banks, can I assume that it is not something specific to either engine bank, such as bad fuel injector O rings or O2 sensors but that more air is making its way to the intake manifold than is being measures by the MAF sensor, which then makes the A-F ratio lean (as the amount of fuel injected is computed based on the MAF)? In other words, something between the MAF sensor or throttle body and the top of the intake manifold where it splits to the engine banks. Could it be O2 sensor(s) because the fuel trim is calculated based on their data?

I am attaching live data from BlueDriver. The driving file doesn't have bank 2 fuel trims but the idle file does, and they are similar to bank 1.

It is definitely not the MAF sensor as I recently replaced it in response to the same code but it reocurred.

 

As far as I know, there is a specific code for LTFT's that are too high too low. That stated, a maf sensor failure with a maf code is likely, especially if both banks are reporting pretty close high LTFT's.

Grab a MAF from a local auto parts store to test, then it fixes it, decide if you want to roll the dice on an aftermarket one or buy an OEM one.

If it was O2 sensors they would likely throw a code for lazy performance (the ECU during warm up actually goes through a specific cyclic change in injector duty cycle that it looks for in the O2 sensors to check that the O2 sensors are working proper).

Double check that all vacuum lines are routed and not leaking (theres all of 3 to 4).

 

I recently replaced it. It's definitely not the sensor. Will update the initial post

 

Do you have an aftermarket intake?

 

No, the original that came with the truck

 

How many miles on the truck?

 

Did you replace the MAF sensor with an OEM unit, alot of the aftermarket ones aren't particularly accurate.
Have you smoke checked the intake for vacuum leaks?

 

I think there is, but it sets at like 30%+
Which is kind of high IMO.

 

No, aftermarket -- but the previous (OEM) was doing the same thing

You mean just quickly scanned whether there are holes along the intake? If yes, yes, the only thing that is giving me some suspicion is the PCV hose, as the clamps seem like they've seen better days

 

158K

 

Those number scream vacuum leak to me.

 

is that the least unfavorable scenario? easiest to fix of all possibilities?

 

Depends where it is.
If it’s a hose, yes.
If it’s the actual intake, not so much.

Did you use new gaskets when you rebuilt the engine?

 

Now that I looked at the numbers I'm not so sure, fuel trims should improve while driving if it's a vacuum leak.

I'd do a VE test next.
https://www.otctools.com/ve

 

Yeah, I didn’t even see the trims in the file above.
That file is way to big for my small phone screen.

You are right, they don’t improve.
They seem pretty sporadic to me?

 

yes

 

why is that?

 

Because there is less vacuum when the engine is turning more rpm.
It also has to do with the throttle blade angle.

 

but doesn't that assume that the vacuum loss volume is constant regardless of the RPM? I can't see how that would be, if you have a hole in your intake somewhere, I can see how it would draw more air at higher RPMs. Am I getting this wrong?

 

There's 2 reasons you typically should see an improvement in fuel trims at higher RPM if a vacuum leak is causing a lean condition:

Vacuum in the intake manifold is lower thus the amount of un-metered air entering through the leak is lower.
There is more airflow through the engine thus the un-metered air from the vacuum leak represents a smaller percentage of total airflow.

Now if there was an air leak between the MAF sensor and throttle body this would not be the case as higher airflow would draw more un-metered air in although this would be unusual on the 4.0L due to the design of the intake and the MAF sensor being right in front of the throttle body.