Hesitation on acceleration

[BigJase88]

Hi so i have owned my 200d CLA for about a year. It is a 2018 2.1 diesel turbo 136bhp automatic 7g. Mileage is 57k miles

It has always had a hesitation on acceleration but it only crops up now and again.

So if say i do a weeks worth of short journeys and then take it a longer run. Im sitting in 7th at say 60mph and i floor it and it kicks down it will hesitate and accelerate very slowly for around 1second then it will give me full power.

It only does this after i have been pootering about for a few days. The rest of the time when i floor it then it responds no problem at all and gives me full power when requested.

No i am just wondering if it is doing a dpf regen and then when i mash the throttle into the floor there is a delay in coming out of dpf regen mode before giving me full power. When it gets stuck in this hesitation phase when it clears a puff can be seen coming out of the exhaust. Not sure on colour but looks sooty.

Which is strange as i have had diesels before and they dont have a lag when coming out of a regen.

Or is it not that at all? Is something coked up with pootling about and the puff of soot or smoke is just the car clearing it's lungs.

Any input is appreciated

Thanks

 

[Bobby Dazzler]

Your transmission is adaptive, it learns your driving style and adapts to it. If you have been driving sedately then it will react more slowly, smoothly and progressively to accelerator pedal inputs, even quite meaningful prods of the pedal. Once you’ve done that a few times then it knows that you intend to do it and its reactions will sharpen and delivery a quicker response. Until you start driving sedately again.

 

[BigJase88]

Your transmission is adaptive, it learns your driving style and adapts to it. If you have been driving sedately then it will react more slowly, smoothly and progressively to accelerator pedal inputs, even quite meaningful prods of the pedal. Once you’ve done that a few times then it knows that you intend to do it and its reactions will sharpen and delivery a quicker response. Until you start driving sedately again.

When i floor it it's not the reaction of the gearbox that is sluggish. It kicks down no problem it then just sits and doesnt pull as it should for about a second. Then it goes as would be expected.

If you have ever driven a honda old school vtec it feels like waiting for vtec to kick in. nothing nothing.... something

 

[Bobby Dazzler]

Your transmission is adaptive, it learns your driving style and adapts to it. If you have been driving sedately then it will react more slowly, smoothly and progressively to accelerator pedal inputs, even quite meaningful prods of the pedal. Once you’ve done that a few times then it knows that you intend to do it and its reactions will sharpen and delivery a quicker response. Until you start driving sedately again.

PS this is the basis of the much suggested “gearbox reset” or “ECU reset” on Internet forums. Holding the accelerator pedal to the floor with the ignition in position II is said to reset something, but it doesn’t.

It fools the car into thinking that you are a car thief escaping capture from Police Interceptors and so it gives you it’s sharpest responses until it realise that you’re just nipping to the Co-op for bread and milk and goes back to normal.

Not sure whether cars as new as yours are so naive so the above may or may not temporarily sharpen its responses. What will work though is putting your foot to the floor and holding it there a few times in relatively quick succession. It won’t reset anything though

 

[Bobby Dazzler]

When i floor it it's not the reaction of the gearbox that is sluggish. It kicks down no problem it then just sits and doesnt pull as it should for about a second. Then it goes as would be expected.

If you have ever driven a honda old school vtec it feels like waiting for vtec to kick in. nothing nothing.... something

It could be an issue but it could equally be explained by the car using a gentle map for the accelerator inputs. It’s controlled by software (using maps) and so can be adapted to change the character of the car.

 

[BigJase88]

It could be an issue but it could equally be explained by the car using a gentle map for the accelerator inputs. It’s controlled by software (using maps) and so can be adapted to change the character of the car.

It must be said. When this happens it is generally the 1st hard acceleration of that drive. After this initial sluggishness then it is as sharp as a tack again.

It is annoying though and can be quite dangerous performing an overtake at times

The car has been on a STAR machine and presents no fault codes except one about outside air quality sensor inoperative which i doubt would affect the engine

The car does have driving modes

ECO
SPORT
INDIVIDUAL
COMFORT

I set it to Individual. Comfort engine / gearbox and sport for the steering feel.

Sport mode is just too harsh on the gear changes and revs way too much for town use.

 

[Bobby Dazzler]

It could be an issue, but it just sounds like the ECUs adapting to me.

 

[BigJase88]

It could be an issue, but it just sounds like the ECUs adapting to me.

It has done it since i got it 10k miles ago. Just wondered if anyone had experienced the same and could maybe confirm if it is a simple "charachteristic" of the car

 

[Bobby Dazzler]

It has done it since i got it 10k miles ago. Just wondered if anyone had experienced the same and could maybe confirm if it is a simple "charachteristic" of the car

I have experienced it very occasionally in several cars, albeit in different models with completely different engine and transmission. My wife experiences it more as she drives even more smoothly than me.

 

[BigJase88]

I have experienced it very occasionally in several cars, albeit in different models with completely different engine and transmission. My wife experiences it more as she drives even more smoothly than me.

The car i came from was an Audi A3 TDI with S-tronic [dsg] and dare i say it that it was a better gearbox no such issues with that.

I do feel the Mercedes 7G is rather more lets say "agricultural"

It's more of a frustration than an issue however

 

[Bobby Dazzler]

The car i came from was an Audi A3 TDI with S-tronic [dsg] and dare i say it that it was a better gearbox no such issues with that.

I do feel the Mercedes 7G is rather more lets say "agricultural"

It's more of a frustration than an issue however

Whilst the performance and characteristics of torque converter transmissions and dual clutch transmissions have converged in recent years, a DSG will always be quicker shifting than 7G. I suspect that the A3 is set up to “feel” sharper - and therefore appear to be more sporting - than a CLA too. The CLA is probably set up to feel more comfortable than sporting - than an A3 too. Accelerator pedal maps are a big part of the way we can be influenced in these regards.

 

[BigJase88]

Whilst the performance and characteristics of torque converter transmissions and dual clutch transmissions have converged in recent years, a DSG will always be quicker shifting than 7G. I suspect that the A3 is set up to “feel” sharper - and therefore appear to be more sporting - than a CLA too. The CLA is probably set up to feel more comfortable than sporting - than an A3 too. Accelerator pedal maps are a big part of the way we can be influenced in these regards.

I wish they had taken that setup through to the suspension. The AMG Line setup is like driving a steam roller