Weird stutter on light acceleration when warm—any ideas?

I’ve got a 2017 3.5 Ecoboost with the 10-speed transmission, sitting at 91k miles. Bought it in November and have put about 4k miles on it since. Ever since I got it, there’s been a subtle stutter during light acceleration, but only when the truck is warm.

It’s most noticeable between 1500–2000 RPM, where it goes “uh uh uh uh uh” before smoothing out. A mechanic said it’s not the transmission and suggested it might be a misfire, but he couldn’t find the issue. I replaced the plugs 3k miles ago and plan to do the boots soon. Anyone experienced this? It reminds me of a dirt bike needing its carb cleaned.

Try using a bottle of fuel system cleaner. It worked wonders for me.

I have the same truck, and while it could be something else, I’m on my third transmission at 81k. Just saying…

Shan said:
I have the same truck, and while it could be something else, I’m on my third transmission at 81k. Just saying…

Yikes. If transmissions are this bad, I might just offload the truck. Not worth dealing with replacements repeatedly.

@Zion
That hesitation and sound are likely the transmission. Someone dumped the truck, and now you’ve got it.

Shan said:
@Zion
That hesitation and sound are likely the transmission. Someone dumped the truck, and now you’ve got it.

Man, I hope not. I had a feeling that dealership was shady. Just sucks that I didn’t drive it long enough to get it warm and notice this issue during the test drive.

@Zion
Unfortunately, Jesus isn’t fixing that transmission.

@Zion
No dealership will admit to a bad transmission. Ever. You just gotta get a warranty and hope for the best.

Vesper said:
@Zion
No dealership will admit to a bad transmission. Ever. You just gotta get a warranty and hope for the best.

I actually took it to an independent shop, and they said it’s not the transmission. Still doesn’t explain the issue, though.

Clean the MAF sensors (there are two). It’s an easy job, but watch a video first and use proper MAF cleaner. Don’t touch the sensor itself, and let it dry completely before reinstalling.

You might also want to:

  • Add a fuel injector cleaner (Royal Purple makes a good one).
  • Try a different gas station. If you’re always using the same one, they might have dirty tanks or bad filters.

Lastly, this transmission is “adaptive” and learns driving patterns. Since you bought it used, have the transmission reset so it can relearn. I reset mine every 30k miles, and it makes a noticeable difference.

Also, start saving for cam phasers if they haven’t been replaced yet. It’s an expensive job you’ll likely face down the road.

@Quade
Thanks for the tips! I was thinking about the MAF sensors but was hoping they wouldn’t be that dirty after just 91k miles. Also, I got lucky—when I bought the truck, it was already in the shop for a new timing chain and cam phasers.

@Zion
They get dirty faster than you’d think. I cleaned mine every 10k miles. It’s an easy job—should only take you about 20 minutes, including dry time.