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2017 F150 King Ranch 5.0 Hesitation

Old 09-16-2018, 08:14 AM
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Default 2017 F150 King Ranch 5.0 Hesitation

2017 F150 King Ranch 5.0, 57K miles.
I started have a hesitation/Mis when feathering the gas pedal. This mainly happens on a level road between 55-70 mph. I had the injectors cleaned, the transmission fluid changed and cleaned and the spark plugs replace.
None of the above corrected the problem. Hesitation/mis is not consistent.
Scratching my head. All the dealership will tell me is they need to keep cleaning and changing items out to find the problem.
For such an expensive vehical, I am dismayed that there is not way to pin point this issue by running tests. Any thoughts?
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Old 09-16-2018, 10:05 AM
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Had a similar problem of a slight hesitation when cruising between 1,500 and 2,000 rpms. Above that or below or when accelerating or idling it was smooth as silk. Another member here posted he was having the exact same problem and what fixed it. His dealer had to call Ford engineering to figure it out and it took 2 trips and a lot of insisting from me for my dealer to go the same direction. It's a hard diagnosis since the computer has no fault codes and all the electronics are working properly.

It was a broken intake manifold runner. The intake manifold runners shaft breaks and it just flops around. This is causing it to block off air to the intake briefly which causes the hesitation. They have to replace the intake manifold since it's all built in. My replacement intake looks slightly different than the original so I think I got a revised part or a 2018 intake manifold. I was able to recreate the hesitation so I insisted on taking the tech for a ride. He felt it and asked how I was able to make it do it so he could take it on a test drive with the IDS connected to the computer. It's fixed now and running great.
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Old 09-16-2018, 12:02 PM
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Thank you for your response RL1990. Do you also have a 2017 5.0? How many miles were on your truck when it happened? Did they give a reason on why the intake manifold runner broke, defective part?
Just curious. This sounds like it all makes sense and all the pieces fit together that this may be the problem on my truck.
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Old 09-16-2018, 12:08 PM
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RL1990,
Also, when the tech finally drove your truck with the IDS connected did he get a reading/code/trouble when he was able to duplicate the problem and figured out it was the intake manifold runner?
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Old 09-16-2018, 12:37 PM
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I have a 2016 5.0 but our engines are the same, Ford didn't make any changes to the 5.0 until 2018. My truck had about 23,000 miles on it when it went in the shop the first time but it started about a month before I took it in. No reason given for the failure, it just broke. Dealer said it was the first 5.0 that came in with that problem. I was able to reproduce it by locking out 5th and 6th gears and drive about 40 mph in 4th.

From what I understand, since IMRC is broken from the controller (you can see it at the back of the engine behind the intake manifold) the air coming in the engine at those revs is enough to move it. Like a flag flapping in the wind. This uncontrolled air flow in the engine is what's causing the stumble. At lower revs it's not a problem because it's in the closed position which is what the computer wants and expects. When accelerating the airflow is strong enough to push it completely open which is what the computer wants and expects.This is why it's only a problem between 1500 and 2000 rpms.

Nothing pointed to the IMRC. The only thing he noted on IDS was something about long term fuel trim was not within specs.

Last edited by RL1990; 09-16-2018 at 12:40 PM.
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