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So, I've noticed a weird behavior that only happens as soon as I start the car, after I release the park break and either switch to R or D, as I slowly start releasing the break pedal, the car kinda jumps off... No weird noises or any lights on the console, it feels like it had some sort of acceleration ready and when I release the break it comes out, but there's really no weird noise or warning when this happens.
 

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But is this expected behavior? None of the previous vehicles I owned acted like that...
I took delivery in December '20 ... I have just over 17k miles and have had several software updates, etc..... With that being said, it has always done this. There is even another thread on this forum about this behavior, and i believe most people believe that this is normal behavior. But if you let the RPM's settle to below 1k before taking off then it does not do this.
 

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it took me a minute.. but i found the original thread.

 

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But is this expected behavior? None of the previous vehicles I owned acted like that...
It's definitely a "glitch". Mine does it as well, as Shogunmark said above, I have to wait for the RPM's to settle before shifting into drive. It doesn't happen in reverse, so I'm able to shift & go when backing up. Also command starting negates the issue as it allows the RPM's to settle before you get in the car.
 

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2021Trailblazer RS AWD Scarlet Red Metallic
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My 21 RS did the same thing. Waiting for the rpm's to settle does help, but it doesn't prevent it all the time. I personally believe the problem is a communication error between the transmission control module and electric parking brake, but I haven't seen an actual fix by GM, so they must be telling owners it's normal.
 

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My 21 RS did the same thing. Waiting for the rpm's to settle does help, but it doesn't prevent it all the time. I personally believe the problem is a communication error between the transmission control module and electric parking brake, but I haven't seen an actual fix by GM, so they must be telling owners it's normal.
Mine does it too. The day I picked it up I almost went through the showroom window. I started it, put it in gear and it leaped toward the building :). Since then it happens occasionally. I find that if I simply start the car and then go through the routing of buckling seat belt, adjusting climate and radio, by those few seconds everything settles down and I avoid the leap.
 

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Mine does it too. The day I picked it up I almost went through the showroom window. I started it, put it in gear and it leaped toward the building :). Since then it happens occasionally. I find that if I simply start the car and then go through the routing of buckling seat belt, adjusting climate and radio, by those few seconds everything settles down and I avoid the leap.
The Trailblazer idles fast for about 30 seconds,then drops.Let it drop before driving.
 

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So, I've noticed a weird behavior that only happens as soon as I start the car, after I release the park break and either switch to R or D, as I slowly start releasing the break pedal, the car kinda jumps off... No weird noises or any lights on the console, it feels like it had some sort of acceleration ready and when I release the break it comes out, but there's really no weird noise or warning when this happens.
I started the original post last year about this behavior. I was told by my dealer it was normal behavior and I should always wait for the RPMS to drop, I laughed!. I told him if it was normal behavior it would occur in all Trailblazers. Best I can determine from others on this forum it happens in less then 10% of vehicles. Good luck if you bring it to a dealer, I have resolved to just live with it. If you find a fix let us know.
 

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I took delivery in December '20 ... I have just over 17k miles and have had several software updates, etc..... With that being said, it has always done this. There is even another thread on this forum about this behavior, and i believe most people believe that this is normal behavior. But if you let the RPM's settle to below 1k before taking off then it does not do this.
I started the original post last year about this behavior. I was told by my dealer it was normal behavior and I should always wait for the RPMS to drop, I laughed!. I told him if it was normal behavior it would occur in all Trailblazers. Best I can determine from others on this forum it happens in less then 10% of vehicles. Good luck if you bring it to a dealer, I have resolved to just live with it. If you find a fix let us know.
I have a TB 22 and the same thing happens to me, I think it's an early start, the engine is simply still warming up, that's why the sudden start or the famous jump.
 

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I have a TB 22 and the same thing happens to me, I think it's an early start, the engine is simply still warming up, that's why the sudden start or the famous jump.
Happens when the engine is warm too. Totally random, approximately 1 in every 10 or so starts, cold or warm. I've had mine for over a year and have had enough start-up samplings to determine the occurrences, frequencies and conditions. Some owners experience it and some don't, it's vehicle specific. I've owned over 15 cars/trucks/SUV's combined, and have driven countless others, not once did I ever experience this behavior and my driving habits have not changed. It is not normal to let your car sit for 20 seconds before you can put it in gear, every time you start it without experiencing a significant lunge forward or reverse, in fact I have never had another vehicle lunge forward when putting it into gear EVER. It sucks but I have learned to live with it, hopefully one day there will be a software update that will correct it.
 

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Happens when the engine is warm too. Totally random, approximately 1 in every 10 or so starts, cold or warm. I've had mine for over a year and have had enough start-up samplings to determine the occurrences, frequencies and conditions. Some owners experience it and some don't, it's vehicle specific. I've owned over 15 cars/trucks/SUV's combined, and have driven countless others, not once did I ever experience this behavior and my driving habits have not changed. It is not normal to let your car sit for 20 seconds before you can put it in gear, every time you start it without experiencing a significant lunge forward or reverse, in fact I have never had another vehicle lunge forward when putting it into gear EVER. It sucks but I have learned to live with it, hopefully one day there will be a software update that will correct it.
oops! Well, I have felt what you say and well it is not always (in my case) and well I have felt that jump when the cars are cold, but I only have a few months with my TB 22 maybe I have not paid so much attention to this, maybe that it is a problem as you say, I will pay more attention to it and soon I will return here to let you know how it went.
 

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oops! Well, I have felt what you say and well it is not always (in my case) and well I have felt that jump when the cars are cold, but I only have a few months with my TB 22 maybe I have not paid so much attention to this, maybe that it is a problem as you say, I will pay more attention to it and soon I will return here to let you know how it went.
Good luck!
 

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Wow I glad other feels this ! My 22 had 8k miles on it and been doing it since I bought it . It’s like a small “jerk” like quick “skip “ or something like that . Almost makes you think something is wrong with the transmission.
 

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Mine does this as well even when I let it idle. In fact I made a post recently. What I do to avoid it is this:
Disengage parking brake when car is in park
Ease a tiny bit off the foot brake
Fully depress foot brake
Put car in drive
No jerk

it’s very convoluted to just get moving but hope it helps.
 

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This happened to mine. I don’t use the parking brake unless on a steep hill. If you get in the trailblazer and throw it in drive right after starting it’ll be more apt to do it. I notice if I remote start the car or give it a good 10-20seconds after starting it doesn’t do it.
 
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