[TheRetiredFordWrench]

I’ll open this by saying; If this were a carburetor engine… but! Some background on me: I retired in 2007 from being a lifetime of working as a mechanic/technician since 1962. I’ve wrenched on bikes, motorcycles, cars & trucks.. gas & diesel. I installed & operated Yamaha’s Emissions Lab, worked for American Honda as a Senior Engineering Technician before returning to working at dealerships as a diagnostic technician/mechanic. But, I’m not a genus or a know it all! I’m working on my 04/05 F150 4.6L to improve performance (like many of us). It has the following: custom made CAI with Ram from in front of the radiator core support, the metered air side is a 3.5” ID MAF housing with a “laminar air” flow grid in front of the OEM MAF (6 pin), 3.375” ID tubing to OEM throttle body. I’ve reprogrammed using DiabloSport’s Intune i3 Platinum tuner, 87 octane custom tune, selecting the Roush CAI option,as well as the Airaid option. Either one has the same results; P0171/174 on hot restart. No matter how the MAF curve is adjusted, it’s just a matter of time before the codes set. No, there are no vacuum/air leaks! My conclusion is: intake air flow is huge compared to stock and greater than either of the listed CAIs. Recorded PID data is:
Both ST’s: +/- 2 to 3%%
Both LT’s: +30%
MAF count: 146.8-171.8
MAF reading: 5.18-5.23 at idle
Fuel pressure at idle: 39psi
My first inclination is to swap the 19# injectors (234k miles) for larger ones. My second choice is to replace the MAF with the 90mm Lightning L54 but that requires installing an IAT separately. So, is anyone ready to “play”?

 

[theterminator93]

First I would suggest that you shut off adaptive fueling in the tune so you only need to monitor STFT and don't have to look at LTFT and STFT to see what's actually going on. You also should get a wideband because there's no way to tune the MAF transfer function at higher load (like WOT) without one. It will also help you dial in the MAF transfer function if it's off severely across the board.

Next I would reinstall the factory MAF and injectors (if possible), programming the tune for them, and letting it idle or run gently for a short time to see what the fuel trims do. That at least will rule out other mechanical gremlins, and allow you to focus exclusively on injector flow table and MAF transfer function adjustments.

 

[TheRetiredFordWrench]

First I would suggest that you shut off adaptive fueling in the tune so you only need to monitor STFT and don't have to look at LTFT and STFT to see what's actually going on. You also should get a wideband because there's no way to tune the MAF transfer function at higher load (like WOT) without one. It will also help you dial in the MAF transfer function if it's off severely across the board.

Next I would reinstall the factory MAF and injectors (if possible), programming the tune for them, and letting it idle or run gently for a short time to see what the fuel trims do. That at least will rule out other mechanical gremlins, and allow you to focus exclusively on injector flow table and MAF transfer function adjustments.

First I would suggest that you shut off adaptive fueling in the tune so you only need to monitor STFT and don't have to look at LTFT and STFT to see what's actually going on. You also should get a wideband because there's no way to tune the MAF transfer function at higher load (like WOT) without one. It will also help you dial in the MAF transfer function if it's off severely across the board.

Next I would reinstall the factory MAF and injectors (if possible), programming the tune for them, and letting it idle or run gently for a short time to see what the fuel trims do. That at least will rule out other mechanical gremlins, and allow you to focus exclusively on injector flow table and MAF transfer function adjustments.

Thank you Brandon. With the OEM intake & MAF reinstalled, (injectors are OEM 19#), all PIDs are normal & O2 sensors are normal with no codes triggered. Hot soak & restart is good, also no codes set or pending. After reinstalling the CAI, I noticed the O2’s switch BUT never above .2-.25 v! I retested for leaks but the system is tight & leak free. I suspect the MAF/metered air side is flowing more than the MAF can compensate for & the tuner can re-curve for. SO… ?

 

[Grog6]

Datalog it and see what the maf voltage is. There's a thread on datalogging, and it lists the stuff to look at.
You aren't going to flow any more air than what flows thru the valves; all the huge tubing in the world won't change that.
I think you were getting air blown across the maf that blew back out, making for a rich condition.

 

[TheRetiredFordWrench]

Datalog it and see what the maf voltage is. There's a thread on datalogging, and it lists the stuff to look at.
You aren't going to flow any more air than what flows thru the valves; all the huge tubing in the world won't change that.
I think you were getting air blown across the maf that blew back out, making for a rich condition.

But P0171 & P0174 are “Lean bank 1 & 2, not rich??

 

[Grog6]

Lean codes are always vacuum leaks.

 

[TheRetiredFordWrench]

Thank you Brandon. With the OEM intake & MAF reinstalled, (injectors are OEM 19#), all PIDs are normal & O2 sensors are normal with no codes triggered. Hot soak & restart is good, also no codes set or pending. After reinstalling the CAI, I noticed the O2’s switch BUT never above .2-.25 v! I retested for leaks but the system is tight & leak free. I suspect the MAF/metered air side is flowing more than the MAF can compensate for & the tuner can re-curve for. SO… ?

Updated data: Yesterday, I spent 3 hours running/resetting the MAF curve and live-streaming data. It seems I misread the O2 data on the intune i3 Platinum tuner! Looking carefully at the O2 data header it reads: “Bank 1 - Sensor 1####” The “#### is the actual data. Bank 2 - Sensor 1####, the same! Easy to misread on the DiabloSport, but the actual script is very slightly smaller! They should fix this!

Now after observing the data here’s what I saw:
When resetting “Keep Alive Memory” & (obviously) code readiness, key on/engine off:
STFTs are 42% (normal)
LTFTs are 0%
Engine temp is fully warmed up
IAT 112F (Florida)
MAF 0g/s
Fuel pressure 39/42psi
O2 0mv

KOER idle:
STFTs begin trending down until stabilizing around +/- 2%
LTFTs begin climbing until reaching +30%
MAF 4.5-5g/s
Fuel pressure stable at 39psi
O2 sensors switch nicely from above.1mv to below .7mv
That’s data with/with out A/C on

Conclusion: knowing that the tuner can only deal with adjusting the MAF curve the injectors are being commanded for a longer pulse width, until the programmed parameters are reached, thus setting P0171 & P0174. Again, I emphasize that I have greatly increased the ability for the induction system to flow greater volume but not changed the ability of the injectors to flow more fuel beyond the rated 19#s. That IS the PCM’s only CONTROL in the system! Everything else is to give feedback to the PCM programming maps. Even shifting the MAF curve isn’t enough to compensate for the increased air flow!

Solution: The PCM has no way of determining what fuel injectors are installed. It only commands a specific pulse width, as per the installed program (OEM). If injectors with greater flow (such as 24# to 42#) are installed, the PCM would go about its business the same way it did before. So, let’s say at a pulse width of .5ms “X” amount of is injected with the 19# injectors, now with higher flow ones, .5ms allows “X+?” amount of fuel and… now the PCM will adjust the pulse width to maintain the ideal air/fuel ratio. The big question is: What size and how do I calculate it? Also, I have not finished “improving” the induction system. I plan on installing a 75mm TB & going to a (same size) higher flow air filter, such as K&N. Those will further increase air flow. I will stick with a naturally aspirated intake. Has anyone else changed injectors and will share that info? What did you install and how did you come to your selection? Thank you again, Tim D

 

[MadMikeyL]

Installing larger injectors is not the correct fix for your problem. You have a slot MAF setup, and you changed the size of the pipe that the MAF is housed in. This means you have to adjust the MAF transfer function. Without doing that, your MAF readings will be off, and you are likely to do damage to your engine. Think about it like this; the actual sensor part of the MAF is pretty small compared to the tube. Most of the air going into the engine doesn’t actually go across the MAF sensor, but if you know the reading on the sensor for a given air mass through the whole pipe, then you can extrapolate those data points to a curve. Now all of a sudden you make the tube bigger. Depending on the situation, either more air is entering the engine for the same reading on the MAF sensor, or the same amount of air is entering the engine, but with a lower reading on the sensor. Either way, the result is that the PCM does not supply enough fuel. The O2 sensors pick up on this, and the fuel trim brings it back in line, but throws a lean code. Now if you add larger injectors, you are simply putting a band-aid on the problem, basically treating the symptoms instead of the cause. The larger injectors will likely bring your idle air fuel ratio back in line, however since the MAF curve is not linear and the injector flow rate is, you will likely wind up lean at higher rpms. To make matters worse, the MAF reading is also used by the PCM to calculate engine load. Since your MAF reading is artificially low due to the larger diameter tube, the PCM will interpret this as lower load, which means it can add more ignition timing. So now you have a car that seems to drive fine, has good fuel trims at idle, but then when you go WOT and it enters open loop, the engine will go lean and the ignition timing will be too far advanced, and that makes a perfect combination for melting pistons! You need to dial in your MAF transfer function, plain and simple. This is basically job #1 in tuning (assuming it is at least close enough to start). Everything else in the tune is dependent on this being correct, and if you start tuning other things, then first off it will never be right, and then when you eventually do come back and correct the MAF transfer function, it will throw off everything else you have done, so you will in essence be starting the tuning process over again.

 

[TheRetiredFordWrench]

Installing larger injectors is not the correct fix for your problem. You have a slot MAF setup, and you changed the size of the pipe that the MAF is housed in. This means you have to adjust the MAF transfer function. Without doing that, your MAF readings will be off, and you are likely to do damage to your engine. Think about it like this; the actual sensor part of the MAF is pretty small compared to the tube. Most of the air going into the engine doesn’t actually go across the MAF sensor, but if you know the reading on the sensor for a given air mass through the whole pipe, then you can extrapolate those data points to a curve. Now all of a sudden you make the tube bigger. Depending on the situation, either more air is entering the engine for the same reading on the MAF sensor, or the same amount of air is entering the engine, but with a lower reading on the sensor. Either way, the result is that the PCM does not supply enough fuel. The O2 sensors pick up on this, and the fuel trim brings it back in line, but throws a lean code. Now if you add larger injectors, you are simply putting a band-aid on the problem, basically treating the symptoms instead of the cause. The larger injectors will likely bring your idle air fuel ratio back in line, however since the MAF curve is not linear and the injector flow rate is, you will likely wind up lean at higher rpms. To make matters worse, the MAF reading is also used by the PCM to calculate engine load. Since your MAF reading is artificially low due to the larger diameter tube, the PCM will interpret this as lower load, which means it can add more ignition timing. So now you have a car that seems to drive fine, has good fuel trims at idle, but then when you go WOT and it enters open loop, the engine will go lean and the ignition timing will be too far advanced, and that makes a perfect combination for melting pistons! You need to dial in your MAF transfer function, plain and simple. This is basically job #1 in tuning (assuming it is at least close enough to start). Everything else in the tune is dependent on this being correct, and if you start tuning other things, then first off it will never be right, and then when you eventually do come back and correct the MAF transfer function, it will throw off everything else you have done, so you will in essence be starting the tuning process over again.

Thanks MadMikeyL;
I’ve been reading about that today and unfortunately, the handheld tuners fall short of doing a total fix! Of course they do! I was afraid that was the correct way.
I called a local tuner in Clearwater, Florida & he charges $450 to set the MAF transfer function. Here’s a few photos of my system.

 

[TheRetiredFordWrench]

Thanks MadMikeyL;
I’ve been reading about that today and unfortunately, the handheld tuners fall short of doing a total fix! Of course they do! I was afraid that was the correct way.
I called a local tuner in Clearwater, Florida & he charges $450 to set the MAF transfer function. Here’s a few photos of my system.

Updated June 23 2022; I’m now looking for a local tuner who can write tunes to the DiabloSport intune i3 Platinum platform. I’m in Largo, Florida. They will be able to install the proper MAF transfer data and revised tune on my i3.