Forget the fact it's on its third suspension at 72,000 miles and it's NEVER left the pavement.
Forget the fact that it's on its 4th set of brakes because the OEM versions are just CRAP and the anti-lock brakes keep warping the rotors. Forget the fact that it gets a paltry 16mpg city and 21-22mpg highway.
The LAST STRAW was replacing the battery a week ago Saturday right before the temperature here plunged to -18.
Who in their right effing minds requires FIVE different socket sizes (3 metric, 2 SAE) just to remove a battery? Why was one battery post Metric and the other SAE?
Ok, past that now. So battery comes out and the onboard computer DUMPS/CLEARS itself within 2 minutes of the battery being disconnected. WTF?
Then, re-connecting the NEW battery the stupid headlight washers decide to give me a nice blue shower.
Who's the bloody bleeping moron at GMC that said "You know, when they re-connect the battery, let's have the headlight washers give 'em a good spritz for a job well done?"
So I remove the battery to see if I'm creating a short somewhere (I wasn't ....) and attempt to re-install the battery. Oops! Got another blue shower once the battery was reconnected.
This is the WORST part though: The stupid thing wouldn't idle when I restarted it after installing the new battery. Kept dying out.
Google is my friend, so I google "GMC Envoy won't idle after changing battery" .... wouldn't you know, up pops the problem: After the computer dumped and cleared itself, it thought it had a nice, clean throttle-body. In other words,it thought it was a brand new car with a nice clean fuel system -- when it wasn't. Wouldn't you know, the onboard computer knows the throttle body is getting dirty over time and "adjusts" the fuel/air mix to compensate. That "compensation" is lost once the computer clears.
So in order to get the stupid thing to run right guess what I had to do? You guessed it, remove the throttle body (which was quite dirty....) and clean it.
That meant --- disconnecting the battery again. OH JOY!!
Disconnected battery, removed Throttle Body and cleaned it. Looked like brand new.
Re-installed Throttle Body (did I mention that took 3 different socket sizes?) and re-connected battery.
Oh yeah, got another nice blue shower. You'd think I'd have learned by the second blue shower? nope, got a third.
Opened door, started vehicle. VAAAARRROOOOOOM!!
Thank the Lord! Went to high idle, stepped down as it should as it warmed up and stayed running at 650 RPM idling as it was supposed to.
Now, I'm all for doing normal maintenance on a vehicle, that don't bother me. What bothers me is when a simple 20 minute task turns into just over 4 bloody hours!!
I've never EVER had a vehicle where the computer cleared itself to the point the stupid vehcile wouldn't run right, simply by disconnecting and installing a new battery.
My 1996 Jeep Cherokee Country didn't do it. Neither did our 1999 Grand Caravan, our 1994 Thunderbird, or event the Wife's 2008 Honda Odyssey.
I don't know what GM was thinking (especially with the headlight showers when re-connecting the battery) but as God in Heaven is my witness, this is my first and LAST GMC vehicle.
Next time you need to replace the starting battery...I suppose now that you know what happens you could connect a small 12V source -- like a motorcycle battery with leads and alligator clamps -- to the terminals while swapping out the big 'un. But there is probably some procedure to avoid all this hassle. Possibly there are small terminals to power just the computer memory while you are changing the starting battery, or saving and reloading the settings.