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Doors unlocking and locking. Loosing speed, RPM jumping to 6. Gas unresponsive. - In that order while driving

999 views 3 replies 4 participants last post by  GIOTAYLOR  
#1 ·
Hi everyone, If I am here, is because I have nowhere else to turn to. I am about to take it to the dealer next week, but thinking that probably they will charge me an arm an a leg and wont be able to fix my issue.
I want to clarify first of all that I took it to 4 mechanics. 3 said nothing was wrong with the car. Never an engine light on.

I bought a used Acadia 2010 with 87k miles, in August 2024, a couple of days later, while driving. The doors unlocked, locked again and lost power.
Similar thing happened a couple of days later.
When this happens and I am going super slow, or almost stopped the car stops. If this happens while I am driving in the freeway or over 30m/h the car does the following:
Doors unlock and lock again. It loses speed (even with the feet on the gas) the RPM go all the way to 6 and you can hear the engine working super hard to move the car, the gas does not respond, and it slows down at least 20 miles less in a matter of seconds. If I let the car be on its tantrum it takes maybe a 30/40 seconds to recover, but if I press the brake, it reacts faster. Once it did the same thing while I was breaking as I was about to turn, and the car just had the doors lock and unlock.
This has happened to me at least once every 3/4 days, except during November /december that I went almost 2 month without issues. And all of a sudden the freeze came in Texas and I had a million issues more. Even one day, that it did the same thing in a matter of minutes 3 time, and left me stranded on the freeway, a message popped in the dashboard "speed limit to 108m/h" I was going 40m/h. This type of message never popped again, that was 2 month ago.
The 4th mechanic I took it to, did a full diagnosis and replaced a few things. Serviced the transmission, changed the fuel pump and monitor, changed the starter, checked battery and alternator, replaced the front axle, (that were giving problems in the direction) replaced the tire sensors and recently replaced another computer (forgot wich one) after the axls he replaced just broke by me doing nothing.
I took it from the mechanic on Thursday and this morning (tuesday) did the freaking tantrum again. He cannot figure out what the issue is, and his colleagues are telling me to sell it, I do not want to sell, I already put too much money on it, I want to first make sure the issue is not fixable.
If after this long story you made this far... you live in my heart rent free! I hope you have some idea of what can it be and I can figure this out.
THANK YOU!
😍
 
#2 ·
Weird, I swear that I responded to this already but I see zero responses. Anyhoo ...

The door lock & unlock thing has been associated with a loss of electrical ground or a low battery state of charge. There are threads on this subject in both the Acadia forum and the Sierra forum.





 
#3 ·
I actually think it's either a ECM or TCM that's gone bad. These symptoms are VERY similar, if not mirroring, the issues I had with my 2009 Malibu LLT V6 with the 6T70 (very similar powertrain across the board).

This was about 2011 or 2012. I first started having intermittent electrical issues, including locks, power windows, security system, etc. Then random power losses or lack of power, also maybe the ignition wouldn't start right away. However, the problems only happened occasionally and the dealer couldn't replicate. Then one day while traveling the Pennsylvania turnpike at about 75 MPH, the engine tried to blow itself up — blew past redline, car kicked like a mule, and I slowed down to about 35-40 MPH almost immediately. Took everything I had to keep it on the road because that initial kick on the curve I was in made me lose traction initially.

Anywho, limped it along at 25 MPH to the nearest exit, which just by chance happened to have a Chevy dealer about 2-3 miles off the highway. Left the car with them and proceeded on my road trip with a rental and picked the Malibu up on the way back 1.5 weeks later. It's been too long, so I can't remember which one they replaced (it may have even been both), but after replacement, I never had an issue again for the remainder I owned the car, which was another 3-4 years.

I would probably start with replacing the ECM, but the TCM in that model year is also known to have issues and could need replacement. However, you really need to know what has already been done to this vehicle to assess whether it's worth putting that kind of money in. For that model year, have the timing chains been replaced? 3-5-R transmission wave plates replaced under the special coverage (now expired)?

If the answer is no, you'll probably be needing those as well before too long, and all of this together is easily a $3-5,000 bill, which is more than what the actual vehicle is worth!