Auto stop/start quandary

Acpantera · September 15, 2021

I know I'm probably one of the few folks that doesn't mind the feature on the new vehicles, and I know a lot of parameters are taken into consideration for it to operate. The only issue I am having is that when the engine does shut off at a red light, the engine only stays off for roughly 30 seconds, and most traffic lights are red for about 60 seconds, it would seem the fuel savings could be increased by staying off for the full duration of the light. Has anyone found a way to extend the "off time"? So far I have operated the truck in ambient temps between 60 to 90 degrees and tried turning off the hvac and other accessories, still haven't been able to extend the off time.

elcamino · September 15, 2021

Its controlled by the ecm and there is no way to change the parameters; Have to live with the way it is. PS, I turn off every start.

Minnvmax · September 15, 2021

Say what?! My 2019 has never turned back on by itself. I have to lift the break or tap the gas. I too turn it off every time I start. Have I really had this truck that long and not sat with it off long enough for this even to happen?

Edited September 15, 2021 by Minnvmax

bdallas · September 15, 2021

My experience has been that if I turn the A/C off, the engine stays off until I take my foot off of the brake. That's true for as long as the red light lasts. I'm sure if I were to sit there too long, the engine would kick back on.

...but if my A/C is on, it kicks back on in 30 seconds or so.

Edited September 15, 2021 by bdallas
add info

redwngr · September 15, 2021

Time limit for the stop portion of auto stop/start is 2 minutes.

If it's starting sooner it's one of the other reasons.

Autostart Criteria

Driver Enabled Conditions that will engage Autostart:
• Driver removes pressure from the brake or depresses the accelerator pedal while the vehicle is in the forward Drive gear System Enabled Conditions that will engage Autostart

Note: If one or more of the following conditions occur, the system will force the engine to restart.
• Economy mode turned OFF
• Brake booster vacuum is less than 40 kPa (6 PSI)
• HVAC inside air temperature changes than 3°C (5°F) (with HVAC Automatic)
• A/C compressor request from HVAC (A/C or Defrost modes)
• Battery voltage less than 11 V,
• Battery state of charge is less than 73% (changes with state of health)
• Driver door status changes to open and driver seat belt status changes to unbuckled (not applicable to vehicles in North America)
• Hood switch status changes to open
• Autostop time exceeded 2 min

If the crank time exceeds 2 s, a manual ignition switch restart will be necessary.

I believe 'Economy mode' refers to one of the modes for the charging system

Acpantera · September 15, 2021

3 minutes ago, redwngr said:

Time limit for the stop portion of auto stop/start is 2 minutes.

If it's starting sooner it's one of the other reasons.

Autostart Criteria

Driver Enabled Conditions that will engage Autostart:
• Driver removes pressure from the brake or depresses the accelerator pedal while the vehicle is in the forward Drive gear System Enabled Conditions that will engage Autostart

Note: If one or more of the following conditions occur, the system will force the engine to restart.
• Economy mode turned OFF
• Brake booster vacuum is less than 40 kPa (6 PSI)
• HVAC inside air temperature changes than 3°C (5°F) (with HVAC Automatic)
• A/C compressor request from HVAC (A/C or Defrost modes)
• Battery voltage less than 11 V,
• Battery state of charge is less than 73% (changes with state of health)
• Driver door status changes to open and driver seat belt status changes to unbuckled (not applicable to vehicles in North America)
• Hood switch status changes to open
• Autostop time exceeded 2 min

If the crank time exceeds 2 s, a manual ignition switch restart will be necessary.

I believe 'Economy mode' refers to one of the modes for the charging system

Thanks for the posting, out of all the stuff I read on the topic yours is the first I have seen that mentions the 2 minute max, maybe mine being the 2.7 has different requirements for the start stop. Perhaps I just haven't hit the just right conditions for the engine to stay off for more than 30 seconds. Also I do want to add that I too shut off the feature when I know I'm in an area where there is a lot of stop signs or when I'm maneuvering around where auto stop make no sense or is a nuisance.

aseibel · September 15, 2021

My wife's 21 Acadia Denali does not have any option to turn it off. Most of the time it doesn't bother me as I don't drive in a lot of traffic with lights due to where we live. If it shuts off at a stoplight, it turns on quick enough not to be an inconvenience. It does turn back on after a certain time. Definitely using the AC keeps the engine on more.

The worst situation I endure is a 4-way stop where I have to wait for someone else to clear the intersection, I may be sitting still for 2 seconds but the engine shuts off in that time, then re-starts. Its teaching me to roll through the stop sign rather than hard-stop it.

redwngr · September 15, 2021

34 minutes ago, aseibel said:

My wife's 21 Acadia Denali does not have any option to turn it off. Most of the time it doesn't bother me as I don't drive in a lot of traffic with lights due to where we live. If it shuts off at a stoplight, it turns on quick enough not to be an inconvenience. It does turn back on after a certain time. Definitely using the AC keeps the engine on more.

The worst situation I endure is a 4-way stop where I have to wait for someone else to clear the intersection, I may be sitting still for 2 seconds but the engine shuts off in that time, then re-starts. Its teaching me to roll through the stop sign rather than hard-stop it.

They will only do one stop/start cycle per stop.

Lift foot off brake just enough to get a restart and it will stay running for however long to continue to be stopped.

Our 2020 Acadia Denali has the stop/start disable switch on the console just ahead of the cup holders.

2021 Acadia OM -- Auto Stop Disable Switch Graphic

aseibel · September 15, 2021

1 hour ago, redwngr said:

Our 2020 Acadia Denali has the stop/start disable switch on the console just ahead of the cup holders.

Well holy &^%$, there it is. I just went out and looked. We do have it. I swore I read somewhere that it didn't exist and I never bothered to look.

I'm pretty used to it shutting off now, and yes, just lifting the foot 90% off the brake it will fire up. Now I don't know what I'll do when driving her vehicle around. My truck is a 15 so I don't have to worry about it at all.

Acpantera · September 17, 2021

Well, Did some test running late yesterday. Engine and tranny up to operating temps, hvac set and maintaining the same outside temp, longest the engine would stay off was about 40 seconds.

Turned the hvac completely off and the engine would stay off for 2 minutes. All normal I guess. Thanks for helping me through it.

Wiggums · September 18, 2021

Keeping your foot firmly on the brakes makes a difference. If you lighten it, the truck thinks you're just slowing down in traffic. I also think having accessories being charged shortens the off time.

Acpantera · September 18, 2021

33 minutes ago, Wiggums said:

Keeping your foot firmly on the brakes makes a difference. If you lighten it, the truck thinks you're just slowing down in traffic. I also think having accessories being charged shortens the off time.

That one I figured out one the first day.

My last car had "auto hold", one feature I kinda miss. Come to a complete stop and you could take your foot off the brake and it stayed put til you hit the gas.

Toolmandbq · September 20, 2021

I got sick of hitting the button every time. Bought the auto stop start eliminator from 4Dtech. Works perfect every time. Took about 30 min to install. They have an excellent step by step video on how to install it. After driving around with it for 2 months I found no change in my mileage. It just eliminates the annoying restart after every stop.