seems to surge at low speed/ coming to a stop

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bessie
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seems to surge at low speed/ coming to a stop

Post by bessie » Tue Nov 19, 2013 10:11 pm

Since the weather turned colder Bessie (09 T-Rex) seems to rev up slightly when I am bringing her to a stop.
She only does this when she is cold, after warming up she seems normal.

Recently had transmission fluid changed, but she was not doing this right after the change.

Any thoughts on what may be going on and a fix??


BowmanvilleX
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Re: seems to surge at low speed/ coming to a stop

Post by BowmanvilleX » Fri Nov 22, 2013 2:28 am

I had the same issue with my T-rex aswell...Clean your throttle body with Mass Air Flow sensor cleaner worked wonders for me

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Fat Steve
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Re: seems to surge at low speed/ coming to a stop

Post by Fat Steve » Fri Nov 22, 2013 8:25 am

Yes this^
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bessie
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Re: seems to surge at low speed/ coming to a stop

Post by bessie » Mon Dec 16, 2013 9:47 am

Update and question- Bessie went to dealer and first had her throttle body cleaned and reprogrammed for $200. As soon as a I got her back she has surging more than ever at low speeds, parking lots. Took her back, and the tech who worked on her seemed not to be able to feel what I was describing.
However this time the computer indicated a faulty throttle body, and a cost of $536 to replace. I negotiated a reduction of that price based on the original non fix. Still I am out over $500. My question is now, while the car would seem to be stopping normally, there still is a very very light rpm pick up coming to stops, especially in stop/go traffic, or a parking lot. If I had not had this problem I would likely not notice this. Not looking at the RPM gauge and stopping or stopping from faster speeds to a full stop everything would seem normal. The tick up is only about .02, it was ticking up nearly .05 before repairs. Does this seem normal?

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Fat Steve
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Re: seems to surge at low speed/ coming to a stop

Post by Fat Steve » Mon Dec 16, 2013 12:32 pm

Did Ford not extend the throttle body warranty on the Trex's like on the Freestyles?
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bessie
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Re: seems to surge at low speed/ coming to a stop

Post by bessie » Fri Dec 20, 2013 6:43 pm

No the throttle body warranty only covers 2005-07 Freestlyles- Not T-rex.
I tried to get Ford to cover under the 12N03 but was not successful.
Still getting that slight uptick, when coming to a stop or in stop/go traffic.
Would likely not notice had I not had the recent throttle body problems.
does a slight uptick in rpm's when coming to a stop, possibly from engine braking seem normal?

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Re: seems to surge at low speed/ coming to a stop

Post by pwschuh » Sat Dec 21, 2013 8:01 am

Would that not just be the transmission down-shifting?
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Re: seems to surge at low speed/ coming to a stop

Post by bessie » Wed Jan 01, 2014 10:52 am

I hope it is just the transmission downshifting or engine braking, but an uptick in the rpm's is concerning, and I don't notice this type of thing on other vehicles I drive. After 2 attempts, 1st they cleaned throttle body, next they replaced throttle body and $600 to fix this at the Ford Dealer I am not real inclined to spend more.

It seems to occur now mostly when engine is cold. I have changed the way I drive, coming to more abrupt stops when possible, and the car doesn't rev up. Can't do that all the time however, like in stop/go traffic.

N3UP
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Re: seems to surge at low speed/ coming to a stop

Post by N3UP » Fri Feb 21, 2014 6:07 pm

If it's just a slight rise in RPMs while slowing, it is probably the transmission downshifting.

My 97 F150 does this noticeably at about 25 MPH.
It is the first vehicle with an auto transmission that I could feel the normal downshift.

Hein
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Re: seems to surge at low speed/ coming to a stop

Post by Hein » Mon Feb 24, 2014 4:31 pm

My 08 does this on occasion and I don't think it is a big deal. Seems more noticeable dropping into 2nd while slowing down. I am close to 50K and planning on changing the transmission fluid. I'm hoping my tranny will appreciate the new fluid and smooth out a bit.

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Fuzzball
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Re: seems to surge at low speed/ coming to a stop

Post by Fuzzball » Mon Jan 01, 2018 1:51 pm

Sorry to resurrect this old thread, but I experienced something strange in my 08 T-Rex yesterday and this is as close as I get on a search.

It snowed in Austin Texas yesterday, kind of a last hurrah for 2017. I was coming to a stop at a stop sign and the vehicle started to slide, so I pushed the brakes to try to get the ABS to not allow locking up. It didn't work so well, but when I got to a stop I noticed the vehicle RPM surging up. Releasing the breaks caused the vehicle to surge forward into the intersection. Luckily there was nobody else around and no issues, but it concerned me that this happened and I wondered if it was a fluke. So, I attempted to cause it again and, sure enough, panic stop in the snow caused a surge in the engine while at a stop.

Is this the tranny downshifting? I want to be able to prepare my wife for this eventuality, but I'm not sure what the underlying cause is.

Any thoughts or known issues that I've missed in my searches?

Thanks,

Kevin
2008 Taurus X SEL - Merlot and Silver
1986 Buick Grand National
1966 Glassic Model "A" Phaeton

pwschuh
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Re: seems to surge at low speed/ coming to a stop

Post by pwschuh » Tue Jan 02, 2018 3:55 am

Not sure what caused the surging, but I would also be concerned about this statement: "... and the vehicle started to slide, so I pushed the brakes to try to get the ABS to not allow locking up"

The fact that your vehicle had "started to slide" means that the brakes were already locked. There is nothing you should ever have to do to "try to get the ABS to not allow locking up." ABS is automatic. It is not something that you have to activate by pushing harder. If the brakes are applied (i.e., your brake lights are on) and the wheel speeds differ, the system should self-activate automatically. I would start with a check of the ABS system to ensure that it is functioning properly.
2008 TX Limited
Silver Birch Metallic/Black leather
WeatherTech floormats all rows
Bought used on 17 Nov 10 with 20,000 miles

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Fuzzball
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Re: seems to surge at low speed/ coming to a stop

Post by Fuzzball » Mon May 28, 2018 2:52 pm

pwschuh,

I got to spend the first 3 months of 2018 in Michigan and had a resurgence of the problem where I would seem to surge forward when stopping in the snow.

I have discovered the cause.

Seems I was not moving my foot enough to the left to only be on the brake, but left my heal on the gas pedal. So, while applying brake, I was still applying gas. When I pulled only my heal up and kept the toes on the brake, I came to a complete stop.

Suffice it to say, I hate snow and cold. Glad to be back in Texas where I can only worry about overheating prolems. ;)
2008 Taurus X SEL - Merlot and Silver
1986 Buick Grand National
1966 Glassic Model "A" Phaeton

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