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2004 chevy trailblazer_lt
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Discussion Starter · #1 ·
So this weekend I had to drive up to the airport in Des Moines which is about a two hour drive on the fabulous four lane. So I set the cruise and sat back, ran great at 72 mph getting about 22 mpg, but I digress. On the few longer downhill stretches I noticed that it felt like the motor was cutting out or kind of chugging down the hill with the cruise set. The tach never moved or anything like that. I know on past vehicles that when the cruise was set the motor would back off to allow for the gain of speed downhill but this one seems like it doesn't back off for more than a second to allow for that speed. I had to pick my mom up at the airport and on the way home when it did it she had this concerned look which I had to say oh it always does this. I am just curious if this is what it is supposed to do or if I should be getting something checked out. Thanks
 

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2004 gmc
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Yes, it does this. I heard a rumor that there's an updated flash that addresses this behavior, but I wasn't sure it was a guaranteed fix, and I don't trust my dealer to touch the vehicle anymore, so I just live with it. Tap the brakes to disengage the cruise until the downhill stretch is over, then reengage.

The controller is blipping the engine to see if it is responsible for the downhill speed increase. The programmers definitely missed their target for the cruise control authority algorithms. Probably the same crew of interns responsible for our unique lug pattern and the insane front driveshaft through the oil pan concept.
 

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2004 chevy trailblazer_lt
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Discussion Starter · #3 ·
Yes, it does this. I heard a rumor that there's an updated flash that addresses this behavior, but I wasn't sure it was a guaranteed fix, and I don't trust my dealer to touch the vehicle anymore, so I just live with it. Tap the brakes to disengage the cruise until the downhill stretch is over, then reengage.

The controller is blipping the engine to see if it is responsible for the downhill speed increase. The programmers definitely missed their target for the cruise control authority algorithms. Probably the same crew of interns responsible for our unique lug pattern and the insane front driveshaft through the oil pan concept.
Well I am glad to hear that it isn't just me, although it is a horrible flaw. Feels like you are going to break something. I think for the most part the same group of interns came up with some pretty fuzzy ideas for our vehicles. Don't get me wrong, I love my Trailblazer but between the EV fan, the lug pattern, this crazy cruise issue, and all the other little tidibits that we all know and love somebody was asleep at the wheel. Maybe they were just trying to be new and different but I believe some of their ideas just missed the mark. Oh well. Thanks Roadie for letting me know that I am not alone!
 

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2003 chevy trailblazer_ls
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Ive felt something similar-- and I take it as the engine/computers way of cutting back fuel as the vehicle speeds up...
Never concerned me... I wouldnt say it chugs-- but I can feel it doing something... I always take it off cruise on downhills anyway...


whats up with out lug nut configuration?
 

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2005 chevy trailblazer_ls_ext
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Is this something that was fixed on the 05+ models? Because I've never noticed anything like that. I just got back from another Phoenix run (about 850 miles total).

The only weird thing that happened to me was down in the low desert (Indio area) while fighting some pretty strong winds, the tranny down shifted and all the lights started to flicker for about 3 seconds. My daughter had one of the interior lights on in the rear and noticed it.
All (so called) gauges seemed fine, and hasn't done it since. Weird!
 

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oh yeah- Indio--- that long hill on the 10 that goes down into indio...
and then the hill OUT of indio with all those windmills...
high winds--- ideal spot for those windmills.
 

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2005 chevy trailblazer_ls
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I have this problem as well, except I know its a problem not "just something it does"
I live in FLAT ohio so when I bought the truck I never was able to notice it. However I went to PA and I noticed a VERY slight surging when on certain downhill runs. I noticed it on runs when the hill was just the right angle, too steep and the truck would just coast and no problem, too shallow where it had to keep the gas on and no problem.

Now however it is FAR more, well for lack of a better word, violent.

Before it was almost a trick of the mind, now it will spill a drink in the cupholder.

Anything to look out for? This isnt something that I would consider even remotely normal.
 

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2004 gmc envoy_slt
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Hey cruise-control-users... My wife has the solution - turn it off! I did, and there was no surging, even when maintaining the same speed as when the cruise was on. Has anyone had success with a reflash? Are there any service bulletins for this yet?
BTW - newbie alert. I have mechanical abilities, but I'm new to the forum so forgive me if I failed to search or missed a thread that answers my questions.:hail:
 

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:hahano: That isn't really a fix. When you pay big bucks for a vehicle everything should work - and work RIGHT!

As for the fix or a TSB, I haven't heard anything more about this on other threads, so I can't say. I will say I've rented several Trailblazers, a couple of Envoys and a Buick Rainer over the last 4 years or so, and I've never noticed this problem on any of them!
 
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