our 19 6.2 10 speed does the same thing, dealer drove it and said can not replicate and normal. Watch the tach bouncing around when it happens...definitely an AFM issue. hate it on these new trucks.
Dealer checked it out, said it is normal. Worst speed for it is 60-65. You can watch on the DIC as it dropped cylinders the mpg spikes, drone and rattle and jerkiness starts, then it loses to much power and more cylinders kick in and and it goes away. Reminds me of my 2012 Avalanche with the 6 speed, afm kicked in to early but you would hear deto , now it is a drone/ rattle. As good as they had the 6.2 8 speed in the 17 it is disappointing to go so far backwards.
2000 miles on our 2019 sierra Slt with 6.2 and 10 speed. So far unless you are drag racing in sport mode the the 6.2 / 10 speed combo is a step backwards from the the 2017 6.2/8 speed setup. Mpg city is lower and highway mpg is 2-4 poorer at least. The truck does not free wheel or coast, requires constant throttle to maintain speed.
After more driving I am convinced it is the 6.2DFM and the new 10 speed. With 2000 miles now this truck just does not coast or free wheel at all like the 2017 6.2 and 8 speed. With the 8 speed you get to cruising speed and back of the throttle and use low rpms and torque, can get anywhere from 22-28mpg highway and just a pleasure to drive. If you try the same thing on the 2019 with the 10 speed as soon as you let back on the throttle it drops cylinders and feels like the brakes are dragging. To maintain speed you have to keep your foot on it all the time at the expense of 2-4mpg. Who at gm does such a lousy job at programming these things? I would take my 8 speed back in a heart beat. The 10 speed goes like snot off the line in sport mode, beyond that I find no redeeming qualities. Baffling how they can go so far backwards with a new model.
My new 19 6.2 has a constant on/off jerkiness and drone when it is dropping cylinders. city or Highway? Just drove to St. Louis and back and it was terrible. It did not do this in the 1st 300 miles but now it is really bad. I just joined to research this and most say it is not noticeable on the new trucks but mine is bad and my 17's with the 6.2 you could not tell. I think I need to take it to the dealer and have it checked out, it is not enjoyable to drive the way it is. Such a quiet truck except for the on/off drone.
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We have owned 2 6.2l 8 speed 1500's, 1 sierra and 1 high country both 2017 with the 3.23GR. Performance and Mpg has been spectacular, 21-22mg over city and hwy. Just replaced the 17 Sierra with a 19 6.2/speed combo. Performance is good if driving aggressive but new fuel management is horrible, drone,lag,stutter. Very disappointing for a new truck and mpg is 17-18 with the same driving. This truck is terrible so far. Going to the dealer and see if this dfm is operating properly or not. Both the 17's were unnoticeable going from v8 to v4 unless you watched the dash. I hope something can be done.
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