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slow speed uncommanded acceleration?

Steve1199

By Steve1199
in Troubleshooting & Recalls

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Steve1199 Enthusiast

Steve1199

Posted
Posted

Odd thing has started to happen from time to time on my 14 silverado.

 

What I've noticed is that about 50-60% of the time, when at slow speeds, like in a parking lot, i am getting some uncommanded acceleration. What i'm seeing is that sometimes, when i give a gentle push on the gas, ie moving away from a stop and then let off the gas to coast, about 40-50% of the time, my RPM drops as soon as i take my foot off the gas and i can feel the truck actually coasting and slowing. the other 50-60% of the time, when i take my foot off the gas, my RPM stays where it was, say roughtly 1200ish-1300ish RPM and at times will actually slightly climb from when i took my foot off the gas. when this RPM hold happens, the truck definitely feels like it is still under power driving and i can at times actually feel it accelerate some. This usually lasts at around 10 seconds before the RPM slowly starts to drop as the truck starts to slow, though still feeling like its under power the whole way as opposed to just coasting.

 

Scenario - creeping in parking lot, go to speed up by pressing on gas lightly and accelerating. as i pass through about 10mph, i let off the gas but the truck keeps accelerating at my previous acceleration rate (and RPM increase) for usually less than 5 seconds even though my foot is off the gas. after that approx 5 seconds, the truck will stop accelerating but feel like it is driving under power, as if i have my foot still lightly on the gas to maintain speed. the truck will then slowly coast to a stop, with the RPM decrease tracking the speed decrease of the truck, with RPM settling to idle as the truck coasts to a stop.

 

i hadn't noticed this before i got my TCM reflashed (failed attempt by dealer to solve my transmission clunking issues, which, are less frequent now, but when they happen, it feelsl like i got bumped by a car behind me, actually got out once to check.....), so, may just be coincidental on that one.

 

I would be less concerned if the truck was consistent, ei, either always dropping RPM and coasting, or always holding speed in a somewhat powered state (with foot off gas). what concerns me is the inconsistency of it.

 

my only thought on cause would be some parameter where the truck sometimes cuts the fuel flow when i take my foot off the throttle and sometimes it doesn't cut the fuel flow.

 

Just not a fan of feeling like i'm not fully in control of what the truck is doing. Between this, the transmission clunking, creaking/popping rear springs, loud dash and a shifting drivers seat at times........19,500 miles....

 

anyone else experienced anything like this or have an explanation? i'm due for an oil change in about two weeks so likely will just wait and bring it up when i go in for that.

CounterMeasure Enthusiast

CounterMeasure

Posted
Posted

Yeah, I've seen this on my truck before. What is most noticeable to me is that if in first gear and slightly accelerating, the acceleration is not linear. The truck will accelerate more and more without a change to the pedal position to get the RPMs up on the way to 2nd because of the big gap between those gears. First vehicle I've had that does this. I've just had to learn to give myself more distance and try to anticipate with the truck isn't going to do what I actually asked it to do.

GMCustomerService Senior Enthusiast

GMCustomerService

Posted
Posted

Hello Steve1199 and CounterMeasure,

 

I am sorry to see that you guys are experiencing acceleration issues with your trucks. If you guys send me your VIN, mileage, contact information, and dealership of choice, I would be more than happy to assist you.

 

Kindest regards,

 

Blair E.

GM Customer Care

nuclearxp Enthusiast

nuclearxp

Posted
Posted

yes, in fact mine does the same thing. the ironic thing, is, it seems to happen most often while at a certain facility in warren for work...

Newell33 Enthusiast

Newell33

Posted
Posted

I've felt something similar, but it's generally the transmission hanging in gear, and then leaping forward once it finally decides to shift. Every time I drive my truck for extended periods and in varying conditions, I get more and more disgusted with the transmission.

Pat Grant Enthusiast

Pat Grant

Posted
Posted

I've felt it, but I don't think it's as much an acceleration thing as it is a deceleration thing......More like the torque converter unlocking when you're slow coasting.

andyhaug Enthusiast

andyhaug

Posted
Posted

Mine is doing this too. Working with the dealership on it. The problem is that it is so inconsistent that they cannot duplicate it. Working on a plan forward. When I traded in the 2000 Silverado I thought I was upgrading. Not what I expected from the company that introduced the first automatic transmission.

GMCustomerService Senior Enthusiast

GMCustomerService

Posted
Posted

I've felt something similar, but it's generally the transmission hanging in gear, and then leaping forward once it finally decides to shift. Every time I drive my truck for extended periods and in varying conditions, I get more and more disgusted with the transmission.

Hi Newell33,

 

We're are sorry you are also experiencing these concerns with your Silverado and would like to look into this further. Please send us a private message with your VIN, mileage, contact info and preferred dealership if you need any additional assistance.

 

Thanks,

 

Patsy G.

GM Customer Care

nuclearxp Enthusiast

nuclearxp

Posted
Posted

Hi Newell33,

 

We're are sorry you are also experiencing these concerns with your Silverado and would like to look into this further. Please send us a private message with your VIN, mileage, contact info and preferred dealership if you need any additional assistance.

 

Thanks,

 

Patsy G.

GM Customer Care

I would presume everyone with this problem has contacted their dealer about it (I have).

 

Whatever you think you must be doing to get some secret troubleshooting data the dealers don't have is giving a false sense of customer support.

EPIC CAJUN Enthusiast

EPIC CAJUN

Posted
Posted

Yep mine does this also when Im in traffic. Its really aggravating/annoying as im on and off the gas quite a bit during rush hour. Sometimes are worse than others and Ive almost rear-ended a few people due to this. I just assumed it had something to do with the torque converter. My dealer wil be aware of this at my next oil change

f8l vnm Senior Enthusiast

f8l vnm

Posted
Posted

I have the same thing in my 14. Between that and the clunking it drives me insane.gm says its normal :)

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