MercedesRat

First of all, thank you to everyone on this forum for helping me decide to buy my glc 43 last month! I've been reading this forum everyday and I love my new car (except for this one issue ).

It doesn't happen every time but occasionally when I am slowing down for a red light and the light goes green before I stop and I try to accelerate my glc 43 starts jerking until I take my foot off the gas for a few seconds. This is more likely to happen if I have the car in sport or sport + however it has happened even in comfort (I never put it in eco!).

I never had this issue on my glk 350 and my partner doesn't have it on her GLC 300. Does anyone know what this might be? I plan to take it in to Mercedes and ask but I'd rather not go in completely ignorant. Thank you!!!

cahiil55k

I have the same exact issue in Sport+ mode on our GLC43. I'm still at under 500 miles so thought it might just be a break-in thing. It normally happens from a complete stop especially if I downshift to 1st gear before punching the gas pedal (don't have to floor it to reproduce problem). The car will "hop" up and down like crazy and it feels completely unsafe to continue. 0-60 is probably like 7 seconds when this happens because the car will just do the jumpy thing for 3 seconds. By "hop", I don't mean tire hop like a 700hp car, but its the hop like a manual transmission bunny hop when a teen is learning how to drive stick shift.

Axel B

Do you have the "stop/start" function disabled? I find the operation of the "stop/start" fuel saver to be a little disconcerting....usually disable it.

cahiil55k

For me, I love the exhaust backfires so I always drive in Sport+ which automatically disables the stop/start. Comfort and Sport do not disable stop/start and wife hates that because she only drives in C.

ajpogi24

Yup, same here..experienced this issue twice already in two weeks after i took delivery.

MercedesRat

Yes, it is just like this. It reminds me of when I was a kid and first tried my parents' old manual car. Do you think something is wrong with the transmission?

Also, like you, I don't really floor it yet since I'm at around 500 miles and read on this forum not to (even though I really want to ).

dejongj

I don't think there is anything wrong with the car, to me this is a characteristic. Done about 4,008 miles in ours now and I can induce or remove this behaviour with my right foot.

To me it feels like the car thinks it is getting ready to stop and downshift, so it preselects the wrong gear if you then all of a sudden change your mind. Doing things manually and drive in Sport+ with suitable oomph and keeping the revs up can totally prevent this from happening as you give the car the suggestion you are ready to go and make a move. I mean if it was a manual and you wanted to make a quick get away you'd keep the revs up as well wouldn't you?

In Comfort this is as good as non existent unless you request from nothing full throttle, an easy right foot and letting the boost do the work will keep it totally smooth in my opinion. Again how I would treat it in a manual.

Also don't forget the other reason this thing can hop. Unlike many auto's this car will actually hit the limiter just like a manual does. So if you don't a manual override it may get confused. But in the end it is much better like that during some spirited corners in my opinion.

rexgold

I have had this happen to me multiple times.. only in Sport+ mode.. does not happen in the Comfort or Eco mode...

cahiil55k

If the jerking is normal, it's not acceptable in my opinion. A car wearing an AMG badge is meant to be capable of going fast and should not shudder or hop like a near-stalling manual transmission. It is quite dangerous too. One time the hopping was very violent for me on a curved highway entrance it felt like I was going to lose control of the steering wheel. Car's going in for cosmetic upgrades next week and I will have the dealer look at the issue. I'll post any updates.

dejongj

The you should drive it in comfort mode and not manually override the transmission. Additionally if you do run it manually then you shouldn't bounce of the limiter.

It is capable of being driven very fast and super smooth.

cahiil55k

It's not bouncing off the limiter, not even close. Hopping starts from about 2500RPM and actually I have to let off the accelerator long before it hits 6K. What's Sport+ mode for if you can't use it reliably? I was sold on the Sport+ mode...the dealer couldn't stop talking about it too - the controlled backfires, the aggressive exhaust note, the sportier feel. If not for that, I'd have been satisfied with a GLC300 and a $12K savings since this is truly a car for my wife and not mine.

cahiil55k

I'm no mechanic so take this with a grain of salt. I've had many forced induction cars in the past and the jerking feels more like misfires than a transmission issue. My guess is it has something to do with the turbos finally spooling up and feeding extra air, and the computer not compensating properly for it in first gear (and maybe really cold weather has something to do with this too, as the issue goes away around 60 degrees F). My transmission never tries to shift when this happens. I've also tested this in true manual-only mode and it jerks just the same.

decorily

Like crabbing/skipping?

MercedesRat

Thank you for the responses Dejongj. Since I'm still under 1000 miles and I'm really trying to baby it (first 70k car ) I have not even used the paddle shifters yet. I'm not manually overriding the transmission. I'm also not going above 4000 rpm and so not bouncing it off the limiter. On top of this I did have this happen once in comfort .

Last night when it happened it was 70 degrees out and a person was taking the crosswalk where I was about to turn. I slowed down to a couple mph and then put the gas back on (was in sport only) and this jerking happened. The road I was turning on was near a police station and with a 30mph limit so I actually just barely applied the gas.

I grew up poor with a 10 yr old car from high school through college and never had this issue (although I had MANY others ). I also haven't had it with several 40k cars since I got out of college and I just don't see how it could be something to just accept. It seems like it has to be fixable, at least I hope so!

I was choosing between the GLC 43 and the Levante but I knew the Levante would have issues like this and I really fell in love (and still am) with the driving characteristics of the GLC 43 and decided that driving feel was more important than impressing ladies with a badge . However, as soon as I hit 1000 miles I plan to leave the car in sport + at all times and this issue will really hurt the enjoyment of my car. I'm taking it in soon and hopefully they'll be able to do something!

MercedesRat

I'm with you 100% here Cahiil55k. It was the sport + that sold me too. I love the sound and I love how even when slowly slowing down from 40 mph for a stop light the car begs you not to stop . It really has no regard for the law!

My partner drives her GLC300 only in sport+ and she's never had this issue. I don't see how it can not be an issue on a 40k car but is a an acceptable characteristic of an AMG. I really love mercedes and I was planning on the GLC 63 to be my next car and so I really hope this is something easily fixable and not just a characteristic like Dejongj said because then it will have to be my last AMG

SmokinBuddha

Could this be the issue?

Moisture in the distributor cap can cause a car to jerk when accelerating. When a car has been parked overnight in cold temperatures, moisture can form inside the distributor cap, causing the engine to misfire when accelerating. A misfire occurs because the engine power is off balance or uneven. Parking a vehicle in a garage or a warmer environment helps prevent moisture from forming.
If the vehicle continues to jerk while accelerating gradually over a prolonged time period, a vacuum leak may be the cause. A vacuum leak occurs when the fuel system creates a vacuum in the engine, causing the vehicle to spring forward when the gas pedal is pushed. The vacuum leak sends an incorrect amount of fuel to the engine, causing the vehicle to jerk when accelerating.
If the vacuum leak is not the cause, a car may also jerk when accelerating if it has a faulty throttle position sensor. This occurs in vehicles equipped with a fuel-injection system. Once the gas pedal is pushed, the data in the sensor allocates a certain amount of fuel to disperse. When the throttle position sensor is faulty, it transmits incorrect data, which in turn sends the wrong amount of fuel to the engine.

dejongj

hehehe, that cannot be avoided and it is shredding the tyres.

The jerkiness can be avoided by choosing the comfort setting, or by keeping a load on the engine. It is controllable by the right foot. If it isn't then perhaps it is something different and we are not experiencing the same thing.

So you are saying this is happening at low speed and with limited application of the throttle, and in comfort mode?

My apologies, I though it was something very different. That doesn't sound right at all. My GLC43 is silky smooth under such circumstances, much more so than the 7G box in my GL.

With the explanation on what you highlighted no, I agree that shouldn't happen. However when you get into Sport+ more on the GLC43 it will be harsh and dynamic exactly how AMG have tuned it. However I've found (now I've got 4,008 miles on ours) that when you push it, and make the demand on load to the car it is also very smooth. When you drive it in Sport+ like you are driving miss daisy it will come across as very unrefined. But that is why there is C mode for those circumstances.

Having migrated from the GL with the 7G this 9G is so refined and smooth. But still rough compared to some of the BMWs I've had, and slow compared to the VAG DSG boxes I have.

Don't leave it in Sport+ all the time, it just doesn't make any sense to do that. it will be annoying to drive it like that all the time. You'll look like a silly fool in my opinion driving with revs way higher than a normal person would select them. If you do, then be prepared to break all speed limits and drive it as intended, or manually override the gear box constantly.

Just my 2 cents.

The GLC300 needs to be driven in Sport+ for it to become responsive, well I assume so as that is how I experienced the 220d and 250d. But that is very different to the GLC43 as it is so much more responsive in C than the others are in Sport+, and as such it has an even more aggressive mapping by AMG for the Sport+ mode which is intended to be driven hard.

I really don't get the 'issue' (well other than that you say it is jerky in Comfort as well which isn't right), you can have smooth and responsive, and you can have the fast forward mode that is Sport+ for ludicrous outright behaviour. Seems to me like best of both world at your finger tips (well if Comfort mode operated as it should).

dejongj

Well that is not right then if you have to let off the accelerator before it hits 6K and it hopes from 2500RPM. Something is very wrong with that.

MercedesRat

Yes Dejongj, when it happens it is like it is stuck in first gear and really really jerking. The kind that shakes the entire car over and over until I don't touch the gas for a couple seconds.

I see your point about the sport + and the slight jerkiness that is inherent with sport+ but I don't mind that and (maybe I'm weird) I even kind of enjoy the feeling that the car really wants me to go faster. This jerking is much more severe than that.

I've mainly had the car in sport or comfort so far. It has only happened in comfort once but since it is in sport more often than comfort I'm not sure that it matters very much which mode it is in.

MercedesRat

Thank you! Maybe it is one of these issues.

dejongj

Yes that doesn't sound right at all. I have not experienced that.

cahiil55k

It just did it going up my somewhat steep driveway. I'll report back here once I get this checked out next week. I'm also going to have them check out an issue with my breaks getting stuck at red lights. Almost feels like the parking brake is activating in Drive. This car does not like red lights.

dejongj

You aren't heavy footed are you? I mean could it be that the hold function is engaging?

cahiil55k

No, I am very light footed on brakes except when applying parking brake in neutral.

decorily

Well I just learned something new.... didn't know you can apply parking brake -presumably by pressing on foot pedal.