auto start stop and two random bumps

[got3fords]

Mine shuts off and comes back on fairly smoothly. I don't notice a thump. But lately it only works on the drive home, not in the morning for some reason.

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[Wolfman00]

Are you saying the thump is felt only in the brake pedal? Mine will shudder slightly when the ASS shuts off and again when it restarts, but that is felt in the whole truck; passengers can notice it too.

yup. exactly. if you have the radio cranked and your wearing thin soled shoes like vans- you can feel it without hearing it.
i need to find ways to isolate things so i can narrow it down.
biggest issue is since these trucks have not been around that long- not enough documentation on issues to help solve small things (or big). thats the one thing that was great about tacomas.

 

[VTRanger]

Mine is pretty smooth, can barely notice the engine is off unless I look at the gauges.

There is typically some hard shifting when I come to a stop, could it be the transmission thumping?

Mine did calm down after it did its learning over the course of the first thousand miles, but guessing you have some miles on yours given the year.

I usually drive in S mode so I don't have to deal with it.

 

[VTRanger]

Mine shuts off and comes back on fairly smoothly. I don't notice a thump. But lately it only works on the drive home, not in the morning for some reason.

Do you have the defrost on in the morning? cause that disables it.

 

[Wolfman00]

Mine is pretty smooth, can barely notice the engine is off unless I look at the gauges.

There is typically some hard shifting when I come to a stop, could it be the transmission thumping?

Mine did calm down after it did its learning over the course of the first thousand miles, but guessing you have some miles on yours given the year.

I usually drive in S mode so I don't have to deal with it.

its not the trans, it tested that out. only does it on ASS. sport, or towing it wont do it, or turning the truck off in park. so its narrows to so thing with the auto start.
i wish more people had the issue so i had something to work from.

 

[VTRanger]

its not the trans, it tested that out. only does it on ASS. sport, or towing it wont do it, or turning the truck off in park. so its narrows to so thing with the auto start.
i wish more people had the issue so i had something to work from.

How mushy are your brakes, I wonder if it could have something to do with that?

 

[got3fords]

Do you have the defrost on in the morning? cause that disables it.

At first, but not by the time I get into town, when ASS would be used.

 

[VTRanger]

At first, but not by the time I get into town, when ASS would be used.

That is odd then. I wonder if the vehicle isn't up to temp.

 

[got3fords]

That is odd then. I wonder if the vehicle isn't up to temp.

It takes me about 25 minutes to get into the traffic where ASS would work. Should be plenty warm by then. Maybe the cold weather is keeping the battery voltage lower?

 

[VTRanger]

It takes me about 25 minutes to get into the traffic where ASS would work. Should be plenty warm by then. Maybe the cold weather is keeping the battery voltage lower?

Could be, I know my truck doesn't like cold weather at all. Was 3 degrees here this morning, it runs like a dog till it warms up.

 

[mailbox4449]

Do you have the defrost on in the morning? cause that disables it.

?

 

[Motorpsychology]

Mine shuts off and comes back on fairly smoothly. I don't notice a thump. But lately it only works on the drive home, not in the morning for some reason.

Same here. There are several conditions that can prevent it from shutting off; Not in Drive, Trailer mode, steering wheel angle, state of charge, ambient interior temp/defr on, etc. I think it might have an interlock for oil temperature below a threshold.

 

[Wolfman00]

i'm still convinced that it has to do with your brake booster vacuum and hydraulic brake pressure in some way.
since you feel it in your pedal, and vacuum is lost when the engine stops....i'm leaning towards some sort of valve that actuates to hold your brakes pressure, or increases it...otherwise we would all be rolling through the stop lights when our engines shut off.

The system allows for the computer to pre-charge the braking system when used with the AEB system, so in the back of my head, i am sure this is possibly the connection.
i have no idea if there is an adjustment, but maybe there is since some people like yourself get a bump and others dont.

All I can relate is that early on, i would feel my pedal move when ASS activated, but there wasnt much of a bump.

im leaning pretty hard on the brake booster or something in that system. i will say- sometimes my brakes are really grabby, sometimes not. pretty inconsistent. that also makes me lean towards it’s something in the brake system.
my next step is jackstands and test is out deeper.

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