GMC Acadia Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1
1.The problem only seems to happen when the ac is on but has happened without the ac on.
When pulling into a drive or coming up on a stop light engine will shut off then start right back up, here lately if it dies when the ac is on it will sometimes give me trouble starting unless i shut the ac off.
2. When sitting at a idle for a bit i will get a message that says reduce engine low oil pressure with the typical dinging sound to let me know..
3. It idles at 600 rpms, took it to the shop and they hooked a computer up and no codes really, but adjusted the idle to 700 and it ran perfect. But once they unhook the computer all the problems come right back

So theres my story any help would be greatly appreciated thanks
 

·
Super Moderator
Joined
·
18,629 Posts
Did they run a check on oil pressure at both idle and running rpm? I believe the engine will shut down if the ECM detects insufficient oil pressure.
 

·
Registered
Joined
·
123 Posts
AC puts a drag on the motor, so any issues with low RPM will usually be emphasized. Low oil pressure... how's the oil level?
 

·
Registered
Joined
·
10 Posts
Discussion Starter #4
The oil level is good, they done a long block swap for me, the problem was before the engine swap and the problem didn't go away after.. not sure what all they checked. Had they checked they would have been scared to let me leave in it, bc anytime the ac is on and u stay off the gas and mak a sudden brake or turn the engine dies, no ac on it seems to run fine
 

·
Super Moderator
Joined
·
18,629 Posts
This 'swap' only happened within the last week or so, right? Did you have the car in a service center for the stalling problem beforehand, too? If so, what did they tell you then?
 

·
Registered
Joined
·
10 Posts
Discussion Starter #6
I did have it in the shop before hand we changed some kind of postion or idle sensor and it didn't help then chains broke.. different motor same problem and its not showing any codes that would cause it
 

·
Super Moderator
Joined
·
18,629 Posts
See if they'll go for a "loaner" ECM and find out if that resolves the issue. It's beginning to seem like an undetectable electronic problem, though someone really good at trouble-shooting might be able to find it.
 

·
Super Moderator
Joined
·
18,629 Posts
Find one from a salvage yard, parts site, eBay, etc. and get it programmed for your Acadia. Programming is VIN-specific. You'll have to get the programming done before it's installed, or the vehicle may not run at all.
 

·
Registered
Joined
·
8,496 Posts
Ill throw this out there since its easy to do.
Disconnect Battery for at least 30 min. Clean the throttle body.

This was a common issue on the Trailblazers/Envoys.
Throttle body was dirty. But the computer learned to make up for this dirtiness.
When owners disconnected battery long enough- the learned parameters were lost.
The TB resorted to factory spec settings.
It worked ok.
But- once the AC came on, and you did slow speed driving. like making a slow turn on a street- or driveway- and coupled with maybe turning the wheel-- the increased load caused engine to shut off.
Restarting the car was no problem.
If you left the vehicle in drive or park and let the car idle- you could see the RPMs go up and down- when the AC compressor cycled on.

The explanation was- the compressor was to come on, the computer commanded extra gas to handle the compressor load, but the dirty TB- reacted too slow because it was dirty, the compressor came on, the sudden load caused RPMs to drop (if it was severe enough- engine died), but the computer saw the issue, commanded compressor OFF, by then the extra fuel reaches engine, the RPMs would rise.
You could literally see the tach go from 600 to 300 to 900 and it cycled over and over,

cleaning the TB and battery disconnect- returned the vehicle to normal operation.
Worth a try.

here is a video of it happening on Trailblazer.
 
1 - 11 of 11 Posts
Top