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Randomly bucking while accelerating

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Randomly bucking while accelerating

Post by DACouture1979 » Sat Apr 16, 2016 3:38 pm

I have a 2007 Ford Freestyle SEL, have had it for about 4 years now and presently has 131,000 on it.

The first CVT transmission went out at 61,000 and replaced with a Ford Factory Refurb, the 2nd went at 93k and again replaced with a Ford Factory Refurb.

I always run either Shell or Exxon gas in it and day before Christmas Eve my wife used the car to pack it while I had to work. She filled it at a Walmart Gas Station and it started bucking/surging like crazy. We piled us all into her Sonata Hybrid (not a fun 12 hour ride) and took it into Carmax when I got back (where I had my extended warranty). They said it was because of a dirty throttle body which I then took and had it cleaned at Ford (hadn't had the 150k service done yet). It seemed to have fixed the problem but randomly every once in a while I still got a buck.

Took back to Carmax, they couldn't replicate the problem because again it's every so often so just to eliminate issues and because it hadn't yet been done to my knowledge I changed out the spark plugs and fuel filter. I also at home recleaned my K&N air filter and mass air sensor.

As it got warmer here the past couple of weeks I have off and on used the A/C and I notice this occurrence is more likely to happen when I run the A/C.

I also notice I have the most likely occurrence of this when the A/C is on, vehicle is using Cruise Control, somewhere between 50 - 65MPH and starting to accelerate while going uphill.

My Freestyle is now outta warranty by about 6,000 miles but I would fight the dealer saying this issue occurred and documented prior to warranty expires and needs to be fixed at cost. The problem is I have no idea what is causing the issue.

I'm thinking the torque converter may be locking up but again it is so random I can't think what might be doing it. No check engine light or code thrown either.

I found this but I'm not sure if it's applicable, any help would be greatly appreciated.

Engine Buck/Misfire at Freeway Speeds on Ford Taurus
The engine may misfire and/or buck while driving at freeway speeds with no fault code stored in the powertrain control module (PCM). This can be caused by an intermittent fault with the camshaft synchronizer assembly. This condition can be diagnosed by monitoring knock sensor data as per Ford service bulletin #05-22-12. Replacement of the synchronizer assembly will be required to correct this concern.
RepairPal Verified
Average mileage: 118,283 (11,200–289,800)
Engines affected: 3.0L V6, 3.0L V6 DOHC, 3.0L V6 SHO, 3.8L V6
14 model years affected: 1993, 1994, 1995, 2000, more

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Re: Randomly bucking while accelerating

Post by Africa_FS_07 » Fri Apr 22, 2016 7:53 pm


The TSB info you quoted is for a Taurus and not a Ford Freestyle, and the years are also way different.

Surging is a fault that comes only from the TB.

In most cases, bucking in these cars have been traced to the Fuel System components in the past (Pump, Filter, plugs, Injector Nozzles, Fuel Pressure Regulator, etc). Since you have changed several Parts and the bucking still happens, i would suspect your Fuel Pump.

We experienced the bucking in ours too back then, it was eventually traced to the Fuel Pump in the right side Tank, not the one on the left. I posted a topic on it back then, i think a phrase from the title is "Continuous DTC A627".....you might try searching for the phrase.

The bucking only happened at highway speeds back then, and not in the City at all. Very annoying.

If you could have access to a Code Reader, you might be able to read the Fuel Pressure figures while driving, i forgot exactly what the PSI figure is at the moment, but there should not be fluctuations in the figure.

Also, the PIDs from the Fuel System while in operation will help to understand what is going on in there (status of Lean and Rich conditions).

i would also check the conditions of the Injector Nozzles too.

Does your Car have the "Information Center" in the Cluster, where you could put the car into "Engineering Mode" and see if there's any DTC store in there?
i wonder who "Voodoo Bob of the Dead Poets Society" is hounding now.....:mrgreen:

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Re: Randomly bucking while accelerating

Post by RVAFreestyle » Sat Apr 23, 2016 5:55 am

'Bucking' or the symptoms usually described as it can be caused by:
1. engine misfires (which can be mechanical in nature, ignition, or fuel delivery).
2. dirty throttle actuators particularly at low throttle and increased loads as the stepper motors attempt to push the butterfly past the carbon build up.
3. vacuum leaks and EGR failures (such as stopped up EGR or stuck part open EGR)
4. Poor fuel pressure, I have seen pump fail only under high load and produce pressure otherwise
5. Camshaft timing either slack in the chain under load or phaser
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Re: Randomly bucking while accelerating

Post by Majickmeg » Fri Jul 01, 2016 1:53 pm

This is probably an issue with the troll body, you can clean it out and see if it won't stick, it al can be reprogrammed at a shop, if it's an issue with the old programming. I was working on mine year and years ago because of the bucking and accidentally broke a plastic piece from the throttle body. I bought a new throttle body, that was obviously clean and it had an updated chip. My car hasn't bucked once since then.

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Re: Randomly bucking while accelerating

Post by atsmith2683 » Mon Apr 09, 2018 9:22 am

Did you ever find out the issue? I am having the same thing happen. The throttle body has been cleaned and new spark plugs installed.

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