Hello,

I recently purchased a new 2021 AMG C43 sedan. I love the car overall; however, I'm having a few problems that I've been unable to solve on my own, and I would like to ask for your help.

When I floor the accelerator pedal in first gear from a stop, the vehicle quickly accelerates up to about 5000 RPM, and then the acceleration rapidly decreases, causing me to jerk forward in my seat. At around, 6000-6500RPM, the vehicle automatically upshifts on its own. This jerk is annoying, and my understanding is I am experiencing it because the engine torque drops off around 5000 RPM (see chart below — source). If I remember correctly, I've experienced this problem in multiple AMG Dynamic Select modes (Comfort and Individual are the only two I've used so far). Also, the problem occurs when the engine and transmission have both warmed up — I don't know if it occurs when either is still cold as I haven't tried it.

One solution I have tried is to manually upshift (via the right-hand paddle) at around 5000 RPM. Sometimes this works, but other times, the transmission doesn't respond (see similar issue a C63S owner reported here). I tried switching the transmission from D into M by tapping the button on the center console with the gears on it, but when I repeated the test, the transmission still responded to my upshift request intermittently. So, the only repeatable solution I've found so far is to pull the upshift paddle twice at 5000 RPM — every time I've done this, the transmission has successfully shifted to second gear.

Has anyone else encountered these issues and found solutions?

Thanks for your help,

@sportsedan89

If the car is under warranty , then take it back to the dealer and have them fix it. Surely there is not going to be any mechanic that would call that issue normal.

If the car, for whatever reason is an import, aftermarket might be your only solution.

Thanks, @waisoserious , for your reply. The car is brand new, and I’ve put about 1,400 miles on it so far. Also, the car is not an import — I live in the USA, and the car is USA-spec.

Before I take it in to the dealership, I’m curious to see if other owners are experiencing this issue, and, if so, whether they have found a solution.

Definitely not normal - I've got a 2019 and when ripping it from a standstill it gets through the very short 1st gear so quick that it doesn't have time to stutter, and the only violent motion is the upshift in Sport+ (as intended)
You already ruled out a cold engine or transmission holding it back, and you are out of the break-in period. I'm also guessing it's not a traction issue
Is the behaviour fine when you hit that same RPM range in 2nd or 3rd?
I would give it a try in Sport and Sport+, but can't imagine it would be any different - It seems something worthy of a warranty visit

Thanks @Silverbird for your reply.

To answer your question, the only shift I’ve noticed the problem on so far is from first to second gear.

In an attempt to identify the root cause of the issue, I did a series of tests yesterday. For each of about 16 different combinations of engine and transmission settings, I floored the accelerator starting from rest. I was unable to replicate the issue — on each test, the transmission dutifully performed a crisp shift from first to second gear (no jerk/lag) a bit below 6000 RPM.

The only time the issue recurred was on my drive home. I completed a right turn at about 20 mph in second gear, downshifted into 1st, and floored it. The car did the same thing I mentioned in my original post — at around 6000 RPM, the acceleration cut out and it jerked me forward before sluggishly shifting into second gear.

Definitely strange if you were fully straightened out after the turn.
I've found that the traction control is hyper aggressive so it'll bog down if I try to punch it just as I finish a right hand turn at an intersection and it sniffs just a hint of traction loss due to a bit of gravel/ice, etc.

Did you try switching the ESP to sport or completely switch it off? I suspect your last test invoked slight wheelspin which in-turn would impact the car's throttle and shift behavior.

Yes, I’ve encountered exactly the same issue on a few occasions. Annoying.

I haven’t taken ESP out of the standard mode (I think it’s called “ESP on”?). While I am a relatively experienced driver, I don’t have any track experience, and I like having all the nannies in place to keep me safe! 😂 It’s unclear to me from the manual exactly how much support I’d lose by switching ESP to “sport,” so I’ve been cautious and have left it in the “on” setting. Can you shed any light on exactly what changes when I go from “on” to “sport?” I get that the ESP becomes more relaxed, but I’d appreciate any additional technical details you can provide.

The ESP Sport setting just allows some amount of wheelspin and will allow the car to twitch a little bit during aggressive handling. The nannies are still there, just not so aggressive. Give it a try, I think you will be much happier with the behavior of the car. The only downside I see is that the car will not engage distronic cruise control if the ESP is switched to sport.

Bet this is your fix. Good luck.

In ESP Sport Handling mode, ESP will only improve stability to a limited degree, meaning it allows some drift angles, before it stabilizes the car, but if the car rotates too much or you don't control the drift with countersteer it will keep you from spinning out. Furthermore, the engine torque is only restricted to a limited degree, so it will allow some wheel spin. Traction control is still on, though, but it just won't intervene at the first sign of wheel spin. Also, if you firmly step on the brakes with AMGs, ESP will temporarily revert to fully on as long as you stand on the brake to help stabilize the car. So if you get in trouble you just need to step on the brakes to get ESP to help you stabilize the car. ESP Sport Handling mode is a nice balance between allowing some play w/o completely dropping all the safety nets. I don't know about the C43, but in the C63 at least the limited degree at which it operates also depends on the drive mode. Specifically in the FL on the AMG DYNAMICS setting, which the C43 doesn't have. There are 4 levels (Basic, Advanced, Pro and Master). Master allows bigger drift angles in Sport Handling mode than Basic. I actually ended up 90 degress sideways accidentally in Master and ESP Sport Handling mode one time, and since then I don't go higher than Pro on public roads, unless I'm driving on a deserted canyon road where I put the car in Race, which puts AMG DYNAMICS in Master. The C43 is hard to get sideways to begin with due to AWD, so Sport Handling mode is still very safe. Recommend you only use it if the roads are bone dry, though, or you have plenty of room to not hit anything or anyone.

Thanks, @////AMG_C43 , I’ll give it a try! I rarely use cruise control, so losing access to that doesn’t matter too much to me.

Thanks for the explanation!

Playing around in the snow, I find the ESP Sport setting is still too conservative, and shuts down wheel spin and drift angle quickly, so I would have no hesitation driving around in that setting (all the safety systems are on - emergency braking, etc.)
I found my previous Audi had a better middle ground ESP setting, unlimited wheelspin, a bit of drift angle but still had the stability control active. Was much less tempted to drive with ESP fully off.

i have experienced the same thing as well. if i'm in manual mode and i take 1st gear all the way before shifting, it basically feels like i missed shifting into 2nd gear (if driving manual). and it basically just loses power.

Also, when shifting to 1st to 2nd manually, are there any bangs? i havent tried it too many times, but it seems like it always fails to make a loud noise.

That's frustrating you're experiencing the same issue.

I only get the bangs intermittently, and they seem to be louder on automatic (vs. manual) shifts and when I have the Dynamic setting selected for the Drive parameter in my Individual configuration.

Your description sounds exactly what I have experienced when I have bumped against the rev limiter in first gear.

If you want to maximize acceleration in these cars, keep it in auto mode with suspension on comfort. (Comfort, Sport, or Sport+ makes no difference if you are at WOT)

Out of curiosity, why the Comfort setting?

The softer suspension setting helps weight transfer to the rear for the best possible traction.

Interesting!

Right, allows the car to squat more and transfer more weight to the rear.

I believe that might be the case. even in manual, shouldnt the car shift up for us? just like it wont downshift if it will damage the car?

No, AMGs have what's often referred to as a true manual mode, meaning it won't upshift automatically in manual mode and instead bump into the rev limiter. This is not damaging to the engine. It'll cut fuel to keep the engine from overrevving. You'll basically bounce of the redline. This is just like in a car with a manual transmission, except in a manual transmission you can do a money shift, which is if you downshift too early and then overrev the engine. This transmission will protect you from a money shift, so that's why it blocks a downshift that would result in overrevving the engine, but it won't automatically upshift, because bouncing off the rev limiter is not damaging anything.

thanks! so sounds like cased closed?? I believe OP is experiencing this as well?? Probably just shifting too late.

I still haven’t identified the root cause of the issue I’ve been experiencing. Yes, I think a late a shift is indeed causing the problem I’ve documented, but my question is “what is causing the late shift?” The suspension of my car was in Comfort mode when I last experienced the problem, so I’m not sure the suspension setting is the root cause. I still need to try adjusting the ESP to ESP Sport, as recommended earlier in this thread, to see if that helps with the transmission issue...