[ZLRob]

I know I'm not the only one who experiences this, but has anyone else currently or in the past actually experienced this issue and found a solution for it (ie is it a tuning issue, is it a stock throttle body airflow issue, or maybe is it even both)? I have searched and searched deep and don't come across any clear cut answers so here we are.

This is the way it feels for me coming to a stop:

If I'm revving up to come to a stop (it feels more prevalent in paddleshift mode once I've downshifted to first gear) everything feels fine up until I come to the light or stop sign, then suddenly as the RPM is coming down on the lower end, I feel the engine wants to somehow overpower my braking then I have to step on the brake harder to override that unfavorable engine behavior. I have really looked at it and do not notice the RPM rising as it occurs, but it definitely feels like some sort of engine torque management issue or something.

Anyone got anything? HP Tuners parameters of interest perhaps? Thanks guys.

[raptor5244]

Originally Posted by ZLRob

I know I'm not the only one who experiences this, but has anyone else currently or in the past actually experienced this issue and found a solution for it (ie is it a tuning issue, is it a stock throttle body airflow issue, or maybe is it even both)? I have searched and searched deep and don't come across any clear cut answers so here we are.

This is the way it feels for me coming to a stop:

If I'm revving up to come to a stop (it feels more prevalent in paddleshift mode once I've downshifted to first gear) everything feels fine up until I come to the light or stop sign, then suddenly as the RPM is coming down on the lower end, I feel the engine wants to somehow overpower my braking then I have to step on the brake harder to override that unfavorable engine behavior. I have really looked at it and do not notice the RPM rising as it occurs, but it definitely feels like some sort of engine torque management issue or something.

Anyone got anything? HP Tuners parameters of interest perhaps? Thanks guys.

I think I know what you are referring to. I experienced what you describe multiple times when coming to a stop. I thought my brakes were failing for a second. It didn't do it all the time but enough to be annoying. I didn't notice a rise in RPM either. No idea...other than a glitch in the tuning.

[ZLRob]

Originally Posted by raptor5244

I think I know what you are referring to. I experienced what you describe multiple times when coming to a stop. I thought my brakes were failing for a second. It didn't do it all the time but enough to be annoying. I didn't notice a rise in RPM either. No idea...other than a glitch in the tuning.

Yeah there you go. It's not an all the time thing but it is definitely noticeable and notable enough for it to be an issue.

I wish someone knew what the heck the deal is with it.

That being said I'm not ruling out the possibility that a vacuum leak exists somewhere but it is not enough to trigger engine codes, or maybe even be notable enough for it to be caught by a tuner. That may be an avenue I pursue to rule that out entirely as I do have access to a low pressure smoke machine.

[raptor5244]

Originally Posted by ZLRob

Yeah there you go. It's not an all the time thing but it is definitely noticeable and notable enough for it to be an issue.

I wish someone knew what the heck the deal is with it.

That being said I'm not ruling out the possibility that a vacuum leak exists somewhere but it is not enough to trigger engine codes, or maybe even be notable enough for it to be caught by a tuner. That may be an avenue I pursue to rule that out entirely as I do have access to a low pressure smoke machine.

The few times I experienced it was quite unnerving since I really had to lay into the brakes. Now that you mention it, it does seem like it could be some sort a vacuum leak or something. Whatever it is, it feels like you describe, like the cars wants lurch forward while you have stand on the brake. It only happens at happens at slow speeds.

[ZLRob]

Originally Posted by raptor5244

The few times I experienced it was quite unnerving since I really had to lay into the brakes. Now that you mention it, it does seem like it could be some sort a vacuum leak or something. Whatever it is, it feels like you describe, like the cars wants lurch forward while you have stand on the brake. It only happens at happens at slow speeds.

It's gotta be either a torque management issue or a vacuum leak issue. Because everything else appears and operates totally sound but it is the strangest thing I have encountered in a vehicle before.

It's sort of scary because like you mentioned you almost have to do a brake stand to make it fully stop, which is not cool at all.

[KSZLE]

I experience this when coming to a stop after a spirited run in track mode. Almost like the car has a mind of its own.

[ZLRob]

Originally Posted by KSZLE

I experience this when coming to a stop after a spirited run in track mode. Almost like the car has a mind of its own.

Interestingly enough, I experience this in any mode, tour, sport, or track. It doesn't matter what mode I'm in, but I can always count on it acting up at some point while I'm stopping during my drive. To be honest, it's pretty damn dangerous feeling.

The best way I can describe it is like a brief moment of runaway throttle as it approaches a stop.

[d15b7]

It sounds like you guys are losing brake boost assist. You aren’t left foot braking are you?

[ZLRob]

Originally Posted by d15b7

It sounds like you guys are losing brake boost assist. You aren’t left foot braking are you?

Definitely not, but that is a potential avenue of failure that I haven't thought of. Are you suggesting the brake booster itself is bad? That still doesn't make sense based on what I'm feeling because all of a sudden I feel the engine rock a bit as it's occurring.

Then again, that could very well be an issue with the booster losing vacuum and making the engine surge with the sudden lean spike... Hmm. Didn't even consider that as a possibility on a vehicle this new.

[ZLRob]

So far here's what I got:

- Checked brake booster check valve tonight. Not leaking whatsoever.
- Checked brake booster itself. Not leaking
- Checked all other vacuum connections to make sure they were not slightly off or whatever the case may be. All good.
- Reinstalled everything, ran it, re- simulated the issue once again. Found the issue occurs mostly while it's around 2000-2500 while coasting to a stop with the brake pedal engaged. No loss of vacuum found while it's occuring according to my iDash gauge always somewhere within high 20's through mid 21's while the issue occurs both before, during and after the event.

So far from what I can see it is a tuning issue.

[Z OH 6]

I've never experienced this in mine.

[ZED SLED]

Could it be something to do with rev matching? I have an M6 but when rev match is on and I come to a stop in 1st, sometimes the throttle will blip but doesn't affect anything as the clutch is in. Maybe the A10 does this too causing the surge?

[KingLT1]

brake torque management

[radz28]

Driver Demand tables?