hesitation while accelerating 50-65 MPH?

2001 FORD EXPEDITION
119,000 MILES • 5.4L • V8 • 4WD • AUTOMATIC
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CA101
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Blew transmission seal was slipping a little bit prior to blowing seal sat for 7 months. Took in to repair they allegedly replaced seal, refurbished torque converter, and replaced some clutches. Gas tank was not emptied or stabilized during storage. gas at half tank when picked up car would shift all gears and no issues intown once it got to highway speeds 50-55 MPH car would buckle a lot, the car felt like if it was bouncing up and down. added half a tank of clean gas and seafoam treatment same symptoms if I fully gas it the bucking goes away with the passing gear once i lift off the passing gear it buckles twice and settles if I get it up to speed 65 MPH and cruise it will not buckle and maintain its speed.

obd2 readings
no codes
Mode$6b failed
EVAP failed
Long term fuel trim bank 1 0
Long term fuel trim bank 2 9.8
O2 sensors showing 99.2 efficiency.
MAF g/s on the dot of what it should be running and idling. have driven 50 miles.
Dec 1, 2022 at 5:26 AM
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JACOBANDNICKOLAS
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Hi,

The idea that it is happening at a higher speed, I question if it is related to the overdrive circuit.

Try this. Turn off the overdrive (switch in the shift lever). See if the same issue occurs.

Next, do you have a scan tool that can read the can-bus? If so, check to see if there are any other modules storing codes.

Here is a link explaining how that is done:

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Let me know if it feels more like an engine issue or the transmission.

Take care,

Joe
Dec 1, 2022 at 11:56 AM
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CA101
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Hi, good morning, overdrive off same issue persist no changes my scanner is not compatible with that diagnostic program.
Dec 1, 2022 at 10:26 PM
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CA101
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Also, I forgot to mention it on the initial post, and I apologize it will also happen if there is an incline and I have to accelerate more so between 30-35 MPH as well but on inclines.
Dec 1, 2022 at 10:28 PM
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JACOBANDNICKOLAS
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Hi,

Thanks for the update. I wonder if it is related to a weak fuel pump. By chance, do you have the short-term fuel trims? You provided the long-term above.

If you haven't already, check the pressure to see if it is on the low side of the specifications. Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I attached the manufacturer's fuel pressure specifications below for you.

Let me know.

Joe

See pic below.
Dec 2, 2022 at 1:16 PM
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CA101
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Hi, yes short terms are -2 varies up to +5 changed bank 2 spark plugs today and coil over plugs with OEM. also changed fuel filter was partially clogged. Long term trim 1 still 0 bank2 now lower at 5. Same issues persist and to add it also clunks if I press accelerator fully and then let off abruptly for like two seconds before settling down.
Dec 3, 2022 at 6:06 AM
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CA101
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Don’t have access to fuel pressure gauge when depressurizing system for gas filter good pressure shot from Schroeder valve for good 4 seconds.
Dec 3, 2022 at 6:07 AM
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JACOBANDNICKOLAS
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Hi,

I would recommend using a gauge. 20 psi would shoot from the Schrader as well as the specs.

As far as the trims, they actually look good. Can you tell where the noise is coming from? Is it loud enough for you to record and upload for me to hear?

Let me know.

Joe
Dec 3, 2022 at 12:50 PM
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CA101
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Will do just have to get a hold of one for Noe car is not moving after replacement of fuel filter the leak at the fuel rail increased it used to leak little droplets and was capped off previously but now it drips excessively causing hesitation from get go ordered new motor craft replacement will install when it arrives and check fuel pressure after correcting Schaefer valve leak.
Dec 6, 2022 at 2:31 AM
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JACOBANDNICKOLAS
  • Experienced Mechanic
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Hi,

Thanks for the update. Let me know if the leak repair eliminates the hesitation. I'm interested in knowing.

Take care,

Joe
Dec 6, 2022 at 7:25 AM
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CA101
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Will do thank you.
Dec 6, 2022 at 7:41 AM
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