2017 GT350 With Hesitation On Acceleration, No Engine Codes

[NaughtyCar]

I have had a 2017 GT350 since new (Sept. 2016) with 68k miles and have generally been happy with it. No mods, and no leaks, burning oil or other issues but over the last year has developed the unpleasant habit of hesitating or stumbling on acceleration usually about 5k RPM, but sometimes as low as 4k, and especially in 1st, 2nd, and 3rd gears.
I drive the car only on the street and never been on track but do find my way up the MPH on some of the back roads here...
Sometimes it goes away completely but is usually present. There are no codes generated but sometimes it is so bad that the "stumbling" continues for several seconds and the engine idiot light comes on, but no codes on diagnostic checks.
It also has a slightly loopy idle at times but not as often as the stumbling.
I took it to the dealership and they replaced the output yoke & bolts from transmission as per the TSB that was generated but this did not fix either problem.
Any ideas as to the problem?

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[TonyNJ]

Fuel filter, pump, or some other fuel delivery restriction?

 

[MiamiGT350]

I believe the service interval for fuel filters is 2 years / 30k miles. It would be a good first suspect. Have you noticed mpg take a hit?

Also check your serpentine belt.... maybe it is slipping or should be replaced.

The dealer didn't do any sort of investigation of the actual issue? What did they say or recommend?

 

[WItoTX]

Add spark plugs to the list along with the items above to check.

 

[First Stang]

Traction control?

 

[coz0502]

It also has a slightly loopy idle at times but not as often as the stumbling.

I had a stumbling idle on my GT and it turned out to be a dirty throttle body and/or air flow sensor in the intake. Cleaned both and issue was resolved, there was quite a bit of gunk on the cloth after cleaning. I did not have stumbling at higher RPMs though. But its a zero cost thing you could check out.

Good luck.

 

[NaughtyCar]

OK, will check those basics. The Ford dealer (I have extended warranty) didn't do jack and did not even test drive to check my complaints - which I found out when I picked the car up.

 

[loco_GT350]

You might want to also have the dealer check out this TSB:

19-2090-pdf.350830

I had a similar issue as you and it turned out to be the output shaft flange nut. From what you have written above it does not sound like the dealer replaced this.

 

[NaughtyCar]

My bad, I did - just did not use the right terminology. I have to assume they did what they said but I have an independent mechanic that will tell me and check out the other recommendations.

 

[NaughtyCar]

OK, just a wrap up: the dealership had NOT replaced spark plugs and replaced with OEM as well as changed fuel filter. One of the porcelain jackets on one of the plugs had a small crack non-displaced and looked to be the issue.
Anyway, just replaced both yesterday after ordering the parts on Amazon and it runs crisp with no hesitation and clean crisp throttle response.
Problem FIXED!!!

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