2021 3.5 Ecoboost Preignition FMEM Limit, Injector Cut, Hard Cut

I've been having a very intermittent issue with hitting the Preignition FMEM Limit / Injector Cut on my 2021 F150 3.5 Ecoboost and after taking classes from Elite Tuned and The Tuning School, I'm still unsure on how I should proceed with this particular issue. The issue can occur several times in the same day, but I can also go months without it occurring. I have attached a log showing a normal WOT pull in 4th gear and a WOT pull in 4th/5th where the issue occurred along with the tune file this most recently occurred with.

What normally happens is during a WOT pull at high RPMs I will feel that the engine is slightly down on power, presumably due to the high KR seen when this occurs, I'll get a flashing check engine light, and when I pull the code it is usually P0303, but I have also seen P0305 and P0306. My truck only has 15K on it, and the spark plugs were replaced with 1 heat range colder NGK Ruthenium 95605 gapped at 0.024", the issue was also present with a different set of the same NGK plugs gapped at 0.028"

Any advice or recommended reading on how I should address this issue would be greatly appreciated, searching preignition FMEM limit isn't giving me any results.

Attachment 143227
Attachment 143228

Can you post your stock .hpt file?

Russ Kemp

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Originally Posted by Russ K

Can you post your stock .hpt file?

Russ Kemp

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Stock file attached below:

Attachment 143263

Try this tune. I see that your throttle is closing. On a 2021 Explorer ST 3.0 EcoBoost, in order to prevent the throttle closing, I had to lower the 3634 table by 50%.
Not sure what works on your Truck, as the Explorer ST has a vacuum controlled waste gate, and you have an electronic waste gate.

Not sure about the changes you made to the indicated torque tables. On the 2021 Explorer ST, after using the Torque Inverse Calculator and lowering, then raising the
indicated torque tables & let the calculator fill in the inverse tables, there was no change in the desired air load or the throttle opening. All that happened was either the
vehicle went into limp mode, or the spark timing was jacked causing a high idle. Now the Explorer has the stock torque & inverse tables, and is making 16-19 psi with the
throttle staying open.

What octane fuel are you using? Use 93 if you can find it.

As for the trans, I didn't touch it. But there are a lot of things I would do differently.

Russ Kemp

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Originally Posted by Russ K

Try this tune. I see that your throttle is closing. On a 2021 Explorer ST 3.0 EcoBoost, in order to prevent the throttle closing, I had to lower the 3634 table by 50%.
Not sure what works on your Truck, as the Explorer ST has a vacuum controlled waste gate, and you have an electronic waste gate.

Not sure about the changes you made to the indicated torque tables. On the 2021 Explorer ST, after using the Torque Inverse Calculator and lowering, then raising the
indicated torque tables & let the calculator fill in the inverse tables, there was no change in the desired air load or the throttle opening. All that happened was either the
vehicle went into limp mode, or the spark timing was jacked causing a high idle. Now the Explorer has the stock torque & inverse tables, and is making 16-19 psi with the
throttle staying open.

What octane fuel are you using? Use 93 if you can find it.

As for the trans, I didn't touch it. But there are a lot of things I would do differently.

Russ Kemp

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On the stock tune, I would see larger throttle closures down to 40?. Getting 3634 dialed in better did help to reduce the severity of the throttle closures and this did seem to improve my issue for a little while when I was targeting a lower desired load. I've been trying to find a good balance between keeping the throttle almost fully open and maintaining good turbo response. Lowering 3634 enough to get the TIP actual to match the TIP desired when the throttle is fully open, does seem to make the turbo response noticeably slower.

In previous revisions, I was hitting a hard limit at 2.2 air load, rescaling the indicated torque tables and IPC tables up to 2.5 allowed me to go past 2.2 load. The issue I've been having with intermittently hitting the Preignition FMEM Limit, Injector Cut, and Hard Cut existed prior to all those changes.

I only use 93oct from stations that have been verified to have good fuel. I can get 100oct locally but it's not cheap. With how intermittent this issue has been, it's hard to get a definitive answer on whether or not any changes actually help, but I could try running 100oct for a few months to see if it still happens.

The vast majority of the trans changes I made were following the instructions in the 10R80 courses from The Tuning School and Elite Tuned. Their courses seem more geared towards 10R80 transmissions in 2020 and older vehicles, and my 2021 is missing some tables that prevent me from following their recommendations exactly as written. Is there a particular category of trans changes that you would advise against?

Look at how I did some trans tuning for Dramex72 for his 2020 F150 10R80 in the trans section.

Russ Kemp

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Originally Posted by Russ K

Look at how I did some trans tuning for Dramex72 for his 2020 F150 10R80 in the trans section.

Russ Kemp

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Can you Email me, Have a few questions [email protected]

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Originally Posted by Christian Gomez

Can you Email me, Have a few questions [email protected]

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Post your questions on a new thread. That way it will help others as well.

Russ Kemp