RS5 - idle RPM flare (surge) when coming to a stop

A5/S5/RS5
#41

Comparing to my post above you will see under transmission I have revision H03, whereas yours is H01.

I think that is it, as my car does not have the issue.

#42

It could be the mechatronic unit potentially. Maybe check with a specialist of those for the update and repair (even though it is not broken) the way I see it.

#43

dhuddleson, I have somewhat the same issue you have, I would call it an increased idle when initially coming to a stop. This is on the 2014 engine with 26K miles I just installed, along with a 25k 2015 transmission. I have JHM stage 2 software in both.
My 2013 S5 3.0t with DL501 behaves a lot different, throttle off it definitely cuts the fuel until you get to the idle rpm range and then adds whatā€™s needed to keep it at idle. RS5 seems like it adds a little fuel above idle early and then brings it back to an idle after pretty much coming to a complete stop. Granted I only have about 50mi on the car so far but Iā€™ll have to do some more investigating. Iā€™m out of the country for a while and I when I get back I need to drop the engine down 6" as it is to install a new A/C compressor (dam, should have put a new one in before I installed the engine).
My transmission scan, although I think it is the engine software (emissions related).
Address 02: Auto Trans (J217) Labels:| 0B5-927-156.clb
Part No SW: 8T0 927 156 H HW: 0B5 927 156 K
Component: 0B5 42 FSINAR H03 0005
Revision: --H03ā€”
Coding: 000001

#44

There is only a very small difference between @dhuddleson 's engine scan and mine, though.

If it was the transmission, as I have the latest mechatronic unit in my car, it could be the H03 0010

#45

Thanks for your info Mark and TontoLoid. As I understand, regarding the transmission, the North American 2013 is distinctly different from the 2014 and 2015 model years, as the TCU/Mechatronic was modified/upgraded, so you do see a different part # (hardware). I donā€™t know if those later (software) SW updates like the H03 0005 or even 0010 can be applied to the earlier 2013 TCU still in my car. And I wonder even about the engine (ECM) if TontoLoid has a completely different tune/part # since I think his is a European car. I think USA and Canada will likely be similar specs, but do they change from 2013 to 2014 and onward? So many variables that our local Audi Service department may or may not know without asking ā€œcorporateā€ā€¦

#46

Good questions, Iā€™m thinking it is emissions related after run in the ECU. My tranny is all 2015 but even though my engine is out of a 2014, Iā€™m using the original 2013 ECU with it. Mine is not a big surge, but much different than completely no surge in my S5, Cayenne Turbo, RS6 for that matter. Iā€™m wondering if every car has it for the most part in the software but most drivers are use to it and donā€™t really notice it? Maybe for some reason yours is exagerated a little by some other issue? Throttle bodies, O2ā€™s, some sensor (cam, crank, who knows).

#47

Mark, maybe I am just too observant or nit-picky. The ā€œidle upā€ doesnā€™t ā€œpullā€ the car forward or anything, so the gearbox must truly already be fully disengaged clutch-wise. So I am noticing this, but it does not affect driveability or cause concern the car will surge through an intersection.

By the way, I feel your pain for that A/C compressor work. Such a lot of prep work just to get to itā€¦ sounds like dropping the V10TDI in the 2004-2005 VW Touareg just to change O2 sensors!!!

#48

If there are no error readings from the scan, no serious build-up there is nothing else to go by than SW/HW (upgrades). I am a bit of an optimist ā€“ I think it can be trained away: this are adaptive or learning transmission. Take good care of the car change the filters and so on.

I normally drive in auto mode in the city per the manual, as probably mentioned, never noticed it, at least not since I got the new mechatronic unit.

That touches on another usability thing that might play in, actually. There is an interplay between your driving habits and the adaptation of the transmission to them. So, after a while, this will probably not bother you and at the very least you will get used to it if I am just imaginingā€¦

#49

Is your A/C on when this happens? Can you hear the fans? Could be a combination of that AND needing current from the alternator. Mine will do this on occasion and sit at around 900 rpm.

#50

Michel, thank you for your questions and observations. I have tested with and without A/C engaged and have been able to reproduce the behaviour in both modes. It seems if I am ā€œcoastingā€ to a stop sign in a residential area where RPM is around 1200 or so, it stays there until you would expect the DSG clutches to disengage and RPM should immediately drop. But almost the opposite happens, RPM will rise to maybe 1500 or more when I am basically stopped, and then drop to a normal idle speed within a few seconds. But that delay is very obvious.

#51

Hello @dhuddleson. Have you been able to solve this issue? I think I have the same thing. I own Audi S7 4.0TFSi C7.5 with Dual Clutch S tronic and it feels I am having 100% similar issue.

The funny thing is that it gets a bit better when its hot outside or when I get my transmission oil replaced but never fully disappears. I will try to recap this, hopefully someone will revive this thread and enlighten us :smiley:

  1. I start my car cold in the morning, change to D and then change to R. - Now RPMs go up and down between 600 and 1200 about 3 times the same as I would be reving up the pedal quicklyā€¦ When I came to Audi and they did all fluid replacement + clutch adaptation, this felt like stopped or started doing a lot less than before which is good sign.

  2. I go D, drive for example few meters, 2nd gear is never engaged and I go to stop the car behaves normal, never revs up and does what I expect

  3. When I go few meters or whatever and clutch engages 2nd gear and then I go to complete stop, it starts to behave funky again - RPMs dancing from 600 to 1200 when the car is completely stopped as if it would about to die and tries to revive itself somehow lol.

  4. I go more minutes, warm up the engine and transmission and oil and everything and it feels like the problem disappears. Sometimes it feels like it disappears completely, sometimes it feels lik it revs just few tens above 600rpm and then goes back so its just a little tick.

Now few bit more technical observations:

This problem feels like occurs only when 2nd clutch is being disengaged (R, 2) Because Stronic lets you stop with 2nd gear engaged and then when you are only stopped it needs to go to 1st gear.

I was told this is slipping and burned clutch by other 3rd party service specializing in transmissionsā€¦ It definitely doesnā€™t feel like that, the car is always ready even in higher gears and speeds and catches up nicelyā€¦ Also I made oil change about 15k kms again and the oil was not burned at all, everything just fine.

I have few tips what might cause this (sorted by most probable root of cause by my judgement):

  1. Software bug in transmission - however I have no prove since my transmission software (and ecu) were flashed by Audi and the problem still occurs (but itā€™s doing less nowā€¦)
  2. The adaptation of how I drive (Letā€™s talk honestly, I give the car plenty of fast starts and I love to push full pedal and shoot from the exhaust) So I might confuse the transmission that I donā€™t ever want to sup the vehicleā€¦
  3. Maybe itā€™s really slipping clutch, but it doesnā€™t make sense to me as the clutch works just fine in higher speedsā€¦ It is maybe like Sticky clutch if it makes any sense? :smiley:
  4. This sounds strange, but spark plugs could have misfires, given the complicated software and timing
    of burning fuel this could lead to overlook it (But I would probably feel V8 misfire? Dunno my first V8)
  5. As suggested by other people before, battery could be coming to an end and trying somehow save itself? Maybe some other electronic component?
  6. Battery might coming to end of itā€™s life, couldnā€™t see in records if it was ever replaced (2018 model)

Not related, but S-tronic transmission is garbage in terms of durability, but it definitely is much better in sportiness and comfort than the ZF 8speed tiptronic.

Has anyone came to some conclusion or solution?

edit: Apart from you, my problem is that the revs up push the car a bit forward lik a slight hit from some car from behind but thats just itā€¦

#52

Thanks for your messageā€¦ but not really the same behaviour as you are describing. And no, my symptoms/behaviour have not changed since the initial post. I had a new battery installed last year to replace the original (likely dated 2012). and the surging/hanging idle still happens. It does not matter if I have the A/C enabled or not, as some people felt the A/C may have been the cause. And fully warmed up does not necessarily cause the issue to go away. Could it be driving behaviour? Maybe! When you are in residential areas, often you ā€œcoastā€ along to the next intersection, only braking at the last moment. The RPM tends to be sitting in the mid ā€œteensā€ (~1500) as you coast along, and it stays at that for a couple of seconds when you brake to a full stop.

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#53

Hi! Has anyone been able to fix the rpm surge issue? I found a lot of examples of similar problems on the net, but nowhere did I see information about a successful repair. It worries me because I havenā€™t had time to enjoy the car. The problem appeared after a month, shortly after the purchase from the previous owner (the car is an Audi S7 4.0 TFSI)

#54

My biggest guess is Vacuum leak which is super hard to find in such a complicated engine. Please visit a solid car mechanic which is able to take out all the parts from engine and check where the leakage occurs. My car will be in repair shop for a month since 25th February, so I will post update in later March :slight_smile:

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#55

Im keeping fingers crossed for you to get rid of the problem. I will look for a mechanic equipped with smoke generator. Im also guessing that I have a leakage. Example on how can one try to find one: https://youtu.be/ck66uvvfnNw at 43:45

#56

Hello @Glova :slight_smile:

unfortunately, I have neutral news.

The mechanic who is really experienced with VAG vehicles couldnā€™t find the issue even after 2 days of checking. They did smoke tests for the vacuum pipes and hoses, checked engine graphs if something is wrong but everything looks 100% normal.

With mechanic we both agreed that itā€™s either some ECU glitch or there is some issue with some exact periphery on the engine (some sensor probably) so it thinks the engine will die and adds up some RPM to keep it alive, but it actually doesnā€™t want to die :smiley:

If you have the money, find some superhero repair service that specializes in Audi and is not afraid of getting their hands dirty (meaning disassemble the engine space, take down engine and figure out what is going on)

I spoke with other C7 owners (S6, S7) and they told me they have the exact same issueā€¦ I believe itā€™s something you can live withā€¦ But letā€™s seeā€¦