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Discussion Starter · #1 · (Edited)
I thought I had this issue resolved a few months ago, but I find it still happening periodically. I will be making an appointment to have it checked out soon but wondering if anyone else has experienced this. Vehicle leaps forward (or reverse), on start-up when I put it in gear and remove my foot from the brake, as if it was revving too high, but I’ve seen it happen at 1 grand which I believe to be a normal idol. I have also noticed that at times after it’s been through its warm-up ritual the tach will still sit slightly over 1 grand and at times it will have no affect and others it will. If I am in a tight parking spot this “leap” could cause me to hit a car in front of me, or worse a pedestrian. At first I thought it was because I was putting it into gear while it was still going through its start-up ritual. Turns out that is not the case, I have intentional put it into gear while it was in this phase and the vehicle went into gear normally, I’ve been monitoring this very closely the last couple of months and cannot determine a pattern, it seems to happen randomly. It will happen even after a minute or two warm up. It happens very infrequently, maybe 1 in 40 or so starts. The leap is not very aggressive, but enough to get your attention. I have a feeling this will be one of those cases where the dealer cannot duplicate the issue and tells me that everything seems to be working fine.
 

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2021Trailblazer RS AWD Scarlet Red Metallic
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I agree with everything you said including the random 1 in 40 start ups. I also can't determine any pattern to when it happens. My guess would be a communication error or delay when you put it in drive or reverse. Good luck if you try getting the dealership involved because as you pointed out "cannot duplicate the issue" is the most likely scenario, but if by chance they do find something please share because even though it doesn't happen very often it does make you go whoa there, lol.
 
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Discussion Starter · #3 ·
I agree with everything you said including the random 1 in 40 start ups. I also can't determine any pattern to when it happens. My guess would be a communication error or delay when you put it in drive or reverse. Good luck if you try getting the dealership involved because as you pointed out "cannot duplicate the issue" is the most likely scenario, but if by chance they do find something please share because even though it doesn't happen very often it does make you go whoa there, lol.
Nice to know this issue isn't isolated to my vehicle, curious to find out if anyone else here has experienced it. I'm hoping the dealer may have seen others come in for this problem and determined a fix, I know I'm being overly optimistic. Maybe as more of these SUV's get out into circulation someone will figure it out. I guess these are the bugs that come along when purchasing a vehicle fist year out.
 

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2021Trailblazer RS AWD Scarlet Red Metallic
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2021 Chevy Trailblazer RS AWD
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Early on after getting the Trailblazer I experienced what you might be describing. The pattern I detected was that if I hold the brake pedal to start the vehicle and continue to hold the brake pedal before placing the gearbox in drive, I would get the lunge forward as described. It has been remedied by altering my start-up procedure. Brake pedal depressed to start, release brake pedal during warmup then pressing brake pedal again to engage drive.

My suspicion is that since the brakes are electrical assist, the system goes through an initialization process in those first few seconds after engine start. Holding the pedal mucks up the works. Suspicion and speculation only. No facts to back it up.

1.3 l, 9 speed auto AWD
 

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2021 TB Zues Bronze Activ
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Have had the ACTIV model a year now. How not seen this issue at all. 15k miles.
 

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"Leaping" might not be the best word to describe the issue. Our Trailblazer doesn't "leap", it's more like jolt sometimes when you put in in reverse or drive. It only seems to happen after a cold start and doesn't happen after it's been warmed up. Sometimes I feel like it has something to do with the parking brake, like it hasn't fully released even after pushing the button.
 

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Had a similar experience about a month ago, same symptoms, found this thread:

If I let the engine “cycle” (?) and let the needles max out and drop back to zero before settling to their spots, I don’t have the leaping issue.

^ I hope that description made sense.
 

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Discussion Starter · #14 ·
Had a similar experience about a month ago, same symptoms, found this thread:

If I let the engine “cycle” (?) and let the needles max out and drop back to zero before settling to their spots, I don’t have the leaping issue.

^ I hope that description made sense.
I do the same, wait for cycle to complete, idol goes down to 1 grand and on occasion, it will still leap forward, or reverse. As mentioned in my original post, it happens approximately 1 in 40 start-ups or so. So far only two of us here on this forum have reported this happening.
 

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I only notice this "jolt" if i dont let the RPM's settle after starting up. However this is rare for me as i usually use remote start.
 

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I thought I had this issue resolved a few months ago, but I find it still happening periodically. I will be making an appointment to have it checked out soon but wondering if anyone else has experienced this. Vehicle leaps forward (or reverse), on start-up when I put it in gear and remove my foot from the brake, as if it was revving too high, but I’ve seen it happen at 1 grand which I believe to be a normal idol. I have also noticed that at times after it’s been through its warm-up ritual the tach will still sit slightly over 1 grand and at times it will have no affect and others it will. If I am in a tight parking spot this “leap” could cause me to hit a car in front of me, or worse a pedestrian. At first I thought it was because I was putting it into gear while it was still going through its start-up ritual. Turns out that is not the case, I have intentional put it into gear while it was in this phase and the vehicle went into gear normally, I’ve been monitoring this very closely the last couple of months and cannot determine a pattern, it seems to happen randomly. It will happen even after a minute or two warm up. It happens very infrequently, maybe 1 in 40 or so starts. The leap is not very aggressive, but enough to get your attention. I have a feeling this will be one of those cases where the dealer cannot duplicate the issue and tells me that everything seems to be working fine.
Same with mine,worries me I might hit car in front of mine.Does it randomly like you said.My LT is all wheel with 9 speed.
 

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Discussion Starter · #17 ·
Same with mine,worries me I might hit car in front of mine.Does it randomly like you said.My LT is all wheel with 9 speed.
Sounds like there are now 3 of us on here with the same issue. The only suggestion I can give is to keep an eye on your tach, "sometimes" on a cold start mine likes to sit above 1 grand for a while and if I put it in gear it will leap forward. Let it idle for a while (longer than you normally would) or put it in neutral first and tap the accelerator, this drops the rev's under 1.
 

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I only notice this "jolt" if i dont let the RPM's settle after starting up. However this is rare for me as i usually use remote start.
The only time I run across this Leaping issue is when I key start. I have never had it happen using remote start. It also randomly happens to me about once a month. Dealership thinks I am on meds. Im glad to see, Im not the only one
 

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The only time I run across this Leaping issue is when I key start. I have never had it happen using remote start. It also randomly happens to me about once a month. Dealership thinks I am on meds. Im glad to see, Im not the only one
I've basically confirmed mine happens when I don't let the RPMs settle after the diagnostic on start. It never seems to do it otherwise, or when in reverse.
 

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I've basically confirmed mine happens when I don't let the RPMs settle after the diagnostic on start. It never seems to do it otherwise, or when in reverse.
Happens to me too. When I picked up the car the first day I put it in gear to go forward and it took off like a rocket. It happened to me today in a grocery store parking lot. I just have to remember to be sure to keep foot on brake at start, put in gear, then release brake.
 
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