MGBerridge

I have a 2018 Audi S4 Prestige Auto with 3.0 Turbo Petrol engine in the USA. I have an intermittent issue with very poor throttle response. It has now done 6000 miles and the issue has been there from the time I took delivery. I am the only owner it has had.

1) It never happens on a cold start
2) It happens after a warm start about 5 -10% of the time. Throttle response after a warm start is not as good as after a cold start, but the problem I am referring to is not just a slight hesitation.
3) It usually happens immediately after the start but very occasionally while driving
4) The delay can be as much as 4 - 5 seconds. I can open the throttle then count 1 Mississippi 2 Mississippi 3 Mississippi 4 Mississippi with no change to power output then suddenly it arrives with a rush.
5) When the problem occurs, the Idle is smooth but as soon as the throttle is opened the engine slows. It never stalls. 90% of the time, it behaves like any other turbo I have driven.
6) I haven't had a chance to see if it is ambient temperature related as it has been in the 80s or 90s the whole time I have owned it.
7) It happens with light throttle opening, medium throttle opening or foot to the floor
8) It happens with transmission in D, S or M
9) The Dealer has checked it and says there is nothing wrong (being intermittent it is hard to demonstrate). They reset the transmission change settings back to default and recommended I always use S (they believe it is just turbo lag and S increases engine speed and thus turbo response)
10) To me it seems like an engine management issue, with a particular set of engine sensor inputs causing computer confusion and a delay while it works out how to handle the response to the driver input. Like a computer sometimes pauses. Or it is the result of some compromise Audi have adopted to meet emission standards.
11) It is scary because if you are pulling into traffic and suddenly there is no power you are stranded. This has happened a couple of times. Not funny.

Anyone with any ideas?

Tim Pryor

When I first got my B9 I left it in comfort mode and experienced an extremely similar driving demeanor.
You could legitimately floor the car and wait as life passed you by before the thing would take off like a banshee in comfort mode.
With the way I drive I'd definitely call it dangerous and quite a few passengers noticed and questioned why I was driving like a psychopath when I was just trying to join a highway at reasonable speed.

Coming from a B8.5 which had either a bug or a 'feature' that would default the car to comfort every time you got in it (it would display auto or dynamic but would 100% be in comfort unless you went from dynamic through the options back to auto/dynamic)...
I thought I'd just have to live with it. The newer cars allow you to set it to auto and it always runs in auto. It took a couple of days but the car adjusted to my 'lazy cruising and then occasional I want to go now' driving style.

Since the car's adjusted I don't have any problems with it and keep it in auto and it's reacted exactly how I'd expect in almost all situations.
I haven't driven the B9 in dynamic enough to comment if the behavior exists there.

India Whiskey Charlie

I don't know about hot or cold or different conditions but my B9 S4 has very poor throttle response and a very slow revving engine at all times.
It's my first ever turbo engine and I believe we are experiencing it's inherent characteristics which are not necessarily desirable. Very disappointing indeed.

superswiss

Lag seems to be a common complaint these days about current Audis, but I don't agree that it is an inherent characteristics of turbo engines. In the past perhaps, but the Hot-Vee design that Mercedes pioneered with their AMG V8TT makes for quite responsive, naturally aspirated feeling and performing turbo engines. Drive an AMG with the V8TT and you'll find it to be super responsive and not have the traditional lag/surge behavior that's commonly associated with turbo engines and delivers power much more like a naturally aspirated engine, even in Comfort mode. Yes, the S4/5 only have a single turbo instead of smaller, less inertia biturbos, so that'll make a difference, but there's something else going on. Audi seems to deliberately map the throttle to be somewhat lazy/luxurious on the uptake. Comfort/Auto/D seem to have become the new economy modes and to get at least somewhat of a decent response you gonna have to constantly drive around in S and also make sure to put it in S before putting it in M. It's across the board. Even the new RS5 feels sluggish in its response if you need to accelerate suddenly. They just seem to be deliberately mapped to resist sudden changes. Once you've got it up to boil and the car has detected that you wanna hoon around it's more responsive, but otherwise it acts more like a couch potato unwilling to get up and start exercising. Two possible reasons why this is happening. First one is to squeeze out more mpg and second one is I believe we are seeing the first signs of Audi's transition to being more of the luxury brand than a performance brand in the VW Group. Porsche is taking over the latter for the entire group.

RickNY

I know this has been said numerous times in this forum before -- but driving the B9 S4 in D on the transmission instead of S (or M) is a sure recipe for disappointment.. Although it doesn't sound like that is what the OP is experiencing.

MGBerridge

Thanks for the quick and useful responses. That has given me something to think about and experiment with. My driving mode is also "lazy cruising and then occasional I want to go now" so the solution might be the same. I suspect I underestimated how much they seem to want to make all your decisions for you. I assume that S with its higher engine revs would consume more fuel and didn't see the point when doodling around town, but having also experimented with S the response is definitely better all the time.
Thanks again.

RickNY

My experience with using S as opposed to D as far as fuel economy goes -- I've found that "casually" driving it in that mode (and I do mean that in its strictest sense) - led to a fuel economy decrease of maybe 0.5-1 MPG. HOWEVER, in that mode, I am more inclined to drive the car more aggressively - which of course leads to more fuel usage. With that being said, I average 22-23 MPG through a 50/50 city/highway mix of driving -- and as a matter of habit at this point, I always pull the shifter twice into S when I drive the car.. Once I'm on the highway and not in danger of being slowed by traffic, I throw it into D most of the time and then switch back to S as I exit the highway.

Also -- I certainly didn't get my S4 for fuel economy reasons -- although seeing good numbers on a long highway trip I look at as a bonus.

MGBerridge

I agree that you don't buy an S4 for the fuel economy or to drive gently all the time, but if the time from A to B in routine city traffic is the same in S or D, I would incline towards the more economical option as a default. Driving in D encourages me to relax and go with the traffic flow a bit more. However, it feels nicer to drive in S .
Thanks for the suggestions. I'm pleased that it isn't a fault in my car even if I do have to adopt work arounds to beat the system. I suspect that like it has for you, it will become second nature for me.

LaZyB0ne

As everyone else is saying in this thread, the throttle hesitation is "normal" for these cars. I have an A4 Allroad and notice it mostly in D and still feel it in S. And very little in M but then again I tend to try it harder in S or M. It also bad for me when slowing down then having to hit the gas again. Like when your approaching a red light and then it turns green. I tend to account for these delays now and lightly touch the gas until I feel it catch after the hesitation then press the pedal down harder.

There is this thread over in A4 B9 forum on throttle lag you may find interesting to read. This specific post refers to a trick that supposedly reset the throttle map. I don't think this would elimate the hesitation but if you reset it and maybe drove it a particular way you, maybe could get it to feel better.

https://www.audiworld.com/forums/a4-b9-platform-discussion-212/throttle-lag-2938803/page2/#post25196184

if your really looking to resolve it there are a few different mods that are out that sound promising to help throttle response. The one that I'm most interested is the TCU+ transmission tune that DT power just released. There is a good thread here in the B9 S4 forum on the product. From what I read it doesn't completely eliminate the hesitation but supposed to make it a whole lot better.

https://www.audiworld.com/forums/s4-b9-platform-discussion-214/dt-power-new-products-2958683/#post25212012

superswiss

There are also a few types of lag/delays that generally get conflated together. If you bring the A4 into the mix then we have to talk about the dual clutch transmission. In particular your scenario of slowing down and then changing your mind and accelerating again. Dual clutch transmissions work on the principal that they are two transmissions and the currently idle transmission waits in the wings with the next gear pre-selected. But this strategy relies on the transmission to be able to predict what the next gear will be. If you do something that invalidates that prediction like speeding up suddenly again instead of coming to a stop the transmission has to reshuffle and there are also protection schemes kicking in. It might have already de-clutched to prepare for a full stop, but then suddenly it needs to re-engage the clutch. Or you are cruising on the highway in 7th gear and it has pre-selected 6th on the other shaft assuming that you'll eventually slow down, but suddenly you require full acceleration and instead it has to downshift several gears. This all leads to hesitations, lags and delays, especially if the next gear is on the same shaft. One shaft has the even gears and the other one the odd gears, so for example a sudden required downshift from 7th to 3rd will cause quite a delay as it first has to release the clutch and then change the gear on the current shaft. Planetary gear transmission have an advantage there, because they use multiple clutches and bands to select a gear and can generally do that in the same time it takes shifting a single gear up/down. The AMG Speedshift MCT in particular is well known for its instant ability to downshift multiple gears. The new 9-speed even more so than the previous 7-speed. I believe the ZF8 still takes 200 ms to change gears while the MCT is capable of changing multiple gears in less than 100 ms. Dual clutch transmission can shift in something like 50 ms, but only if the next gear is already pre-selected, otherwise it can take 1 second or more to shift. 200 ms sounds fast, but is perceptible whereas 100 ms and less is not.