Throttle surging when braking in first!
Thread Starter
Team Owner
Joined: Apr 2013
Posts: 26,241
Likes: 4,360
From: Chirper Island
Throttle surging when braking in first!
A6 Z51. I have 6000 miles on her (since I bought her in March), but have never played around in Tr before this. Most of the miles have been in Sport Mode, in M, which I have been enjoying tremendously.
Today, I thought I should check it out. I put her in M with the mode in Track. I got to the end of the driveway (1/8 mi. long) while still in first, just being gentle and seeing what would be different, both in the acceleration, and steering (and it was just my driveway). I got to the end of the drive, and braked. Well, the car surged, and it's a good thing my foot was already on the brake. I turned onto the street, and put her in 2nd, no problem, and braked to a stop with no issue. I put it back in first and accelerated to the end of the street and stopped while still in first, and it surged again.
I put it back in Sport and did not have any issues. Disconcerting, to say the least!
Has anyone else encountered this?
Today, I thought I should check it out. I put her in M with the mode in Track. I got to the end of the driveway (1/8 mi. long) while still in first, just being gentle and seeing what would be different, both in the acceleration, and steering (and it was just my driveway). I got to the end of the drive, and braked. Well, the car surged, and it's a good thing my foot was already on the brake. I turned onto the street, and put her in 2nd, no problem, and braked to a stop with no issue. I put it back in first and accelerated to the end of the street and stopped while still in first, and it surged again.
I put it back in Sport and did not have any issues. Disconcerting, to say the least!
Has anyone else encountered this?
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
Its not surging, its just not slowing down when you let of the throttle when it kicks into 'performance shift mode.' Its a little weird at first because you expect it to slow down when you let off the gas, it will do it in 2nd and 3rd as well if you take it near redline WOT and get off the throttle.
Also if you downshift it will sorta 'rev match' and if you are used to the car slowing down when you manually downshift down a gear with no throttle you will be in for a surprise as well. Takes some getting used to..
Also if you downshift it will sorta 'rev match' and if you are used to the car slowing down when you manually downshift down a gear with no throttle you will be in for a surprise as well. Takes some getting used to..
Thread Starter
Team Owner
Joined: Apr 2013
Posts: 26,241
Likes: 4,360
From: Chirper Island
No. This is when I was almost at a stop. Virtually when I was a only a couple mph. Both times it was when I did not perform a down shift. I was already in first and then came to a stop. It is not the same as when the engine revs when you down shift.
I did not play around with it further at that point. The car literally accelerated of it's own accord.
I did not play around with it further at that point. The car literally accelerated of it's own accord.
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
No. This is when I was almost at a stop. Virtually when I was a only a couple mph. Both times it was when I did not perform a down shift. I was already in first and then came to a stop. It is not the same as when the engine revs when you down shift.
I did not play around with it further at that point. The car literally accelerated of it's own accord.
I did not play around with it further at that point. The car literally accelerated of it's own accord.
I didnt say you downshifted, just it will seem to surge if you do, thats what the 'also' is for.
But if you run up the RPM in 1st it will just hold that RPM when you let off the throttle. If you were just idling along and took off on its own I would call a tow truck and have the dealer take a look at it because something is very wrong. I've driven mine hard around the dragon and a few other mountain roads in 1st gear manual and never had the car try to take off on me.
Tell me exactly what you did and I can try to duplicate it tomorrow, you may have hit on something odd..
Last edited by kp; May 29, 2014 at 12:11 AM.
Thread Starter
Team Owner
Joined: Apr 2013
Posts: 26,241
Likes: 4,360
From: Chirper Island
Thanks. I drove it to the end of my driveway, and when I was almost stopped, at well less than 1000 RPMs, it surged. I wasn't looking at the RPMs, but from the sound it went up at least a thousand, but only for a second (as if I was braking with my left foot and punched the gas). When I stopped in 2nd, and it acted normally. I put it in 1st and drove the last few hundred feet to the end of the street, and expecting the worst, I was not decelerating aggressively, and it did it again. I doubt at that point I was going more than a few mph, just like I was at the end of the driveway.
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
Thanks. I drove it to the end of my driveway, and when I was almost stopped, at well less than 1000 RPMs, it surged. I wasn't looking at the RPMs, but from the sound it went up at least a thousand, but only for a second (as if I was braking with my left foot and punched the gas). When I stopped in 2nd, and it acted normally. I put it in 1st and drove the last few hundred feet to the end of the street, and expecting the worst, I was not decelerating aggressively, and it did it again. I doubt at that point I was going more than a few mph, just like I was at the end of the driveway.
So you didnt accelerate hard before it did it, just rolling along in first coming to a stop?
Track mode, TCS and Active handling were all on? I dont have a Z51 so I dont have any of the PTM modes.
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Racer
Joined: Jan 2014
Posts: 318
Likes: 81
I have to chime in here. I was leaving my dealership a few weeks ago after some warranty work(cosmetics) and accelerated before getting to the end of the drive and I experienced what I thought was the performance shift(auto trans) kicking in and pressed the brake fairly hard to get it to stop. I made the stop then as I pressed the brake the RPM's started to climb to almost 5,000 as I held the brake and shut the car down. I held the brake and restarted the car and everything has been fine since. I started wondering if I had pressed the brake and the gas at the same time with the same foot(never use my left foot unless on the track) but I have never done that in my life and leaves me scratching my head over what happened. Called my dealer and they put a note in their system about what happened with my car just in case it does it again or becomes a systemic issue.
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
After a while I was able to repeat, or at least think I did, what is happening.
If you come to a stop in manual 1st it may not be in 1st and it feels like it downshift at like 10mph and the rev match will kick on and the RPM jumps up. The car will not pick up any speed though and as soon as you touch the brake the RPM drops instantly.
It could also be the torque converter locking up, but you are just crawling along at 5-10mph with no throttle on an even road and then the you feel it downshift or converter lock and then the RPM zings up. I was able to do it at least 10 times.
The mph doesnt go up at all and once you hit the brakes it stops, its like its rev matching just idling along. While it caught me off guard it wasnt anything dangerous, just didnt slow down on its own as expected. Only happens in track mode as well.
If what your car is doing is like Top Beer describes there is something wrong, I never had anything like that happen. If the car is trying to accelerate and you are stopped something is very wrong.
If you come to a stop in manual 1st it may not be in 1st and it feels like it downshift at like 10mph and the rev match will kick on and the RPM jumps up. The car will not pick up any speed though and as soon as you touch the brake the RPM drops instantly.
It could also be the torque converter locking up, but you are just crawling along at 5-10mph with no throttle on an even road and then the you feel it downshift or converter lock and then the RPM zings up. I was able to do it at least 10 times.
The mph doesnt go up at all and once you hit the brakes it stops, its like its rev matching just idling along. While it caught me off guard it wasnt anything dangerous, just didnt slow down on its own as expected. Only happens in track mode as well.
If what your car is doing is like Top Beer describes there is something wrong, I never had anything like that happen. If the car is trying to accelerate and you are stopped something is very wrong.
Last edited by kp; May 29, 2014 at 01:30 PM.
Racer
Joined: Jan 2014
Posts: 318
Likes: 81
After a while I was able to repeat, or at least think I did, what is happening.
If you come to a stop in manual 1st it may not be in 1st and it feels like it downshift at like 10mph and the rev match will kick on and the RPM jumps up. The car will not pick up any speed though and as soon as you touch the brake the RPM drops instantly.
It could also be the torque converter locking up, but you are just crawling along at 5-10mph with no throttle on an even road and then the you feel it downshift or converter lock and then the RPM zings up. I was able to do it at least 10 times.
The mph doesnt go up at all and once you hit the brakes it stops, its like its rev matching just idling along. While it caught me off guard it wasnt anything dangerous, just didnt slow down on its own as expected. Only happens in track mode as well.
If what your car is doing is like Top Beer describes there is something wrong, I never had anything like that happen. If the car is trying to accelerate and you are stopped something is very wrong.
If you come to a stop in manual 1st it may not be in 1st and it feels like it downshift at like 10mph and the rev match will kick on and the RPM jumps up. The car will not pick up any speed though and as soon as you touch the brake the RPM drops instantly.
It could also be the torque converter locking up, but you are just crawling along at 5-10mph with no throttle on an even road and then the you feel it downshift or converter lock and then the RPM zings up. I was able to do it at least 10 times.
The mph doesnt go up at all and once you hit the brakes it stops, its like its rev matching just idling along. While it caught me off guard it wasnt anything dangerous, just didnt slow down on its own as expected. Only happens in track mode as well.
If what your car is doing is like Top Beer describes there is something wrong, I never had anything like that happen. If the car is trying to accelerate and you are stopped something is very wrong.
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
It just holds the speed when it downshifts so you see the rpm jump up, the car isnt accelerating any faster. It appears that even though you have it 1st in manual mode it may be in 2nd until you slow down enough where it does shift into 1st then it rev matches.
If it does accelerate without your foot on the throttle that would be a problem, since it only does it in track mode my assumption would be the car is rev matching so if you are going into a corner it doesnt engine brake and throw the car off balance if you downshift.
Melting Slicks
Joined: May 2001
Posts: 2,596
Likes: 120
From: East Tennessee
It would scare anyone I imagine, with all the electronics and drive by wire in these cars you just never know. Problem when something like that happens you are more concerned with stopping whatever is happening then trying to analyze exactly what caused it.
Racer
Joined: Jan 2014
Posts: 318
Likes: 81
EXACTLY why I started questioning myself if I had my foot on both the brake and accelerator at the same time. It caught me so off guard and was more concerned of controlling the car, I really had no time to surmise what had just happened. Still not sure if it was a fluke or if something went haywire.
Tech Contributor
Joined: Jan 2006
Posts: 4,761
Likes: 240
From: Saint Louis MO
St. Jude Donor '14-'15
EXACTLY why I started questioning myself if I had my foot on both the brake and accelerator at the same time. It caught me so off guard and was more concerned of controlling the car, I really had no time to surmise what had just happened. Still not sure if it was a fluke or if something went haywire.
Racer
Joined: Jan 2014
Posts: 318
Likes: 81
Back in the day, if a throttle cable situation happened 99.9% of time the cable would snap/slip and you would lose acceleration... these days it makes you feel as though it's a 50/50 proposal.
(I am not being literal, I know there are mechanisms and fail safes in place to keep this from happening so put down your torches)
Tech Contributor
Joined: Jan 2006
Posts: 4,761
Likes: 240
From: Saint Louis MO
St. Jude Donor '14-'15
If/when my car tries to kill me, I'll just hold in the clutch....
... All in good fun. 
Racer
Joined: Jan 2014
Posts: 318
Likes: 81
Tech Contributor
Joined: Jan 2006
Posts: 4,761
Likes: 240
From: Saint Louis MO
St. Jude Donor '14-'15
But the Start/Stop button is electronic - no key switch to turn off! ...And the transmission might just not disengage. 
This assumes your car has a killer instinct, of course.
This assumes your car has a killer instinct, of course.