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Unsmooth power on acceleration

Beagleguy
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Beagleguy Enthusiast

Beagleguy

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I have a 2018 GMC Denali 6.2 that is a month and a half old, 2300 miles, 8 speed transmission.  Since new it pulsates or flutters under take off, not a miss but like something is holding it back.  It seems to me a fuel management or torque converter programming issue?  It just does not have a smooth pull as other vehicles I have owned do.  It is smooth at level speed and has no transmission lags or jerks under acceleration or deceleration.  The dealer has no answers since it does not throw a code but understands and puzzled as it is obviously there.  Runs the same on 91 and/or 87 octane, literally no difference.  Love the truck other than the acceleration issue, Any Suggestions Please?  All update bullitons were recently verified and were been done prior to purchase/delivery.

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Supreme Pizza Senior Enthusiast

Supreme Pizza

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51 minutes ago, Beagleguy said:

It seems to me a fuel management or torque converter programming issue?

 

 

Ya, could be one of those items. 

 

Long shot, but you could try turning off traction control, putting it 4x4, selecting a specific transmission gear, try different A/C settings, loosen the gas cap, try holding the brake down slightly while accelerating hard, unplug the battery to reset the computer, etc. 

 

Basically keep trying different things until you find a winner. Chances are, you will be able to find something that either increases or decreases the symptoms, and that will point you in the right direction. 

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KARNUT Senior Enthusiast

KARNUT

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The power all these trucks have it’s not unreasonable to think that torque management and traction control have something to do with it, especially if you don’t have posi traction. Being old enough to remember driving some of the big block trucks prior to the nannies, it was almost impossible to take off without spinning the tires.


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m3n00b Enthusiast

m3n00b

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Mine seems to surge under moderate to hard accelleration like getting on the freeway. Not at wot or slower acceleration.

 

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Jaychevy81 Enthusiast

Jaychevy81

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I have a 2018 GMC Denali 6.2 that is a month and a half old, 2300 miles, 8 speed transmission.  Since new it pulsates or flutters under take off, not a miss but like something is holding it back.  It seems to me a fuel management or torque converter programming issue?  It just does not have a smooth pull as other vehicles I have owned do.  It is smooth at level speed and has no transmission lags or jerks under acceleration or deceleration.  The dealer has no answers since it does not throw a code but understands and puzzled as it is obviously there.  Runs the same on 91 and/or 87 octane, literally no difference.  Love the truck other than the acceleration issue, Any Suggestions Please?  All update bullitons were recently verified and were been done prior to purchase/delivery.

I have a 2018 5.3 with the 8 speed mine does pretty much the same thing. If you get on it it runs through all the gears shifts as it should no issues. But pulling out of my driveway let’s say going down the block holding it at a steady speed. It surges almost like it’s not sure what gear to go into.


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Beagleguy Enthusiast

Beagleguy

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Great suggestions, this truck doesn't have a gas cap, looks kind of like my diesel Ram fill.  I have tried it under full power, partial power, in trailer mode, in a single gear, absolutely 0 difference.  The flutter or pulsation is there at acceleration, not band width or RPM dependent.  I am told there is an onboard system that monitors this, it isn't at a level to register yet you can clearly feel it.  I don't believe it is a traction control issue as it's noticeable under any acceleration, softer mid or hard.  I keep coming back to the fuel management and/or torque converter.  I do get a warble sound out of the transmission under steady driving but it's just a noise, not a performance thing and I think it is normal.  Another way of describing it is it is just not free pulling, like its' being held back.  There is an issue of transmission lag under down or up shift but mine works fine.  My service manager at Wilsonville Chevrolet is getting with the zone tech next week to inquire more deeply.  Note: I had a 2013, 5.3 Silverado 4 X 4 that didn't do this but the truck was under powered on hills and pulling.  Haven't pulled with this truck, just hauled. We have a 2017 Rubicon and a new Subaru Outback in the family, my "Down Town Teddy" Denali is the only one with this issue, LOL!

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Jaychevy81 Enthusiast

Jaychevy81

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Jay, my truck doesn't care what gear but you have described what I feel with your truck; it just doesn't pull freely!

My 2015 with the 6spd acted up to not exactly like this one. But yes I know the feeling it feels like it’s always holding back it could be the grade braking idk. I know that if I am on the highway let’s say getting up to speed. If I let off the gas it will hold that rpm it won’t upshift. Does not do that all the time but usually it does so idk. I have 5500 miles on it now I was going to make an apt at the dealer but I’m sure it’s nothing they will be able to do.


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Dnt Senior Enthusiast

Dnt

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My 2017 6.2 had a weird surge in it when taking off in first couple of gears at low throttle position. It actually felt like it bogged for a second and then would surge forward. It did that from day one until I traded at 19,000 miles a couple months back. Could possibly be the gas pedal but I checked it and I could not discern any play and never really pursued a solution. This 2018 is an identical truck except for being an 18 and a different color. So far over 3000 miles the surge is NOT there and the 8 spd behaves much better on downshifts at slow parking lot speeds. Very pleased with this 18 so far. I might actually keep this one for a few years (Maybe)    

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Nasty Senior Enthusiast

Nasty

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I can say have and do own a few k2 trucks and i hate the 8 spd.   I think thats most of it. For some reason. And if you have the 5.3 with 8spd. Just drive it off a cliff

 

 

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AThomas7782 Enthusiast

AThomas7782

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11 hours ago, BigBlueLB756 said:

The solution to the problem may be as simple as a paint stick.

https://www.gm-trucks.com/forums/topic/167606-gas-pedal-flex-solution/#entry1545219

 

Try not to over-think a solution.

 

 

 

Did that one already. It helped some of the lag, but not the pulsing acceleration. 

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