[habbyw]

Hello guys,

I am desperately looking for answers. I've been to my local Mercedes-Benz dealership about 4 times for this issue and they are unable to tell me with certainty what the issue is. So I'm here to see if anyone else has experienced something similar and if they were able to get it resolved.

About 3 months ago, on a typical day driving to work, I accelerated by pressing the gas pedal down a bit to overtake someone. As the car picked up speed, suddenly it had a violent jerk, almost like I got hit from behind. I thought this was a one off situation as I tried to replicate it again and again and nothing happened.
Over time, the issue became more noticeable and more frequent. It seemed that when I would press the accelerator down to pick up speed fast, the car would violently jerk in 3rd, 4th, 5th and sometimes even 6th gear. The jerking would not stop until I let go of the accelerator. The RPM also stays steady around 4000-5000. At this point is when the car then shifts gears and accelerates as it normally would. There were no check engine lights so the dealership can't scan for any codes. The car is a 2014 CLA 45 AMG that is driven 71000km.

The dealership performed a update to the TCU, and even performed a transmission service however the issue still persists.

After all this they seem to suggest that it is a fault with the dual clutch... but they are not sure.

Since the car is out of warranty, and me having poured a few thousand already into them experimenting fixes, I want to get a better idea of what the issue is and what could be causing it before I sign off on anymore suggestions from this dealership.

So has anyone else had similar issues? What did you do to get it fixed?

 

[jmc]

Wow ... wonder if its rear diff intermittent engagement / power transfer cuz of a developing fault or slippage especially since its occurances are more frequent with time
Maybe unplug the rear diff connection temporarily and run similar condition test drives
No guarantee something else wont pop so its a risk but somewhat a calculated diagnostic risk (and this trick waz posted in other rear diff posts)
My 2cents
Hope it gets resolved

 

[Faux]

I had exactly the same problem last month in my CLA45 - have a tech look at your ‘crank positioning sensor’ - my money is on that!

b

 

[jmc]

If the cps is faulty its effect is only during power phases? Interesting ...

 

[Faux]

Mine only played up ‘under load’ - exactly the same symptoms as outlined by the OP.

 

[jmc]

Which is odd since cps data is a real time feedback data packet for all operational phases ... not sure why its priority would drop when not under power
But if the cps is faulty and giving out of band data during power phases then thats another story
Might even just be a poor contact (loose, oxidation, corrosion) causing a voltage drop and that will give the ecu a heart attack

 

[Faux]

Which is odd since cps data is a real time feedback data packet for all operational phases ... not sure why its priority would drop when not under power
But if the cps is faulty and giving out of band data during power phases then thats another story
Might even just be a poor contact (loose, oxidation, corrosion) causing a voltage drop and that will give the ecu a heart attack

jmc,

they did have trouble diagnosing apparently, luckily a tech was in from Germany and after numerous road tests and a few hours diagnosing they replaced the sensor and my main battery, apparently the voltage was loosing power and not feeding the sensor too (does this make sense? - I have no idea about this stuff)

Anyhow all sorted now, I’m sure I still have all the paperwork if you or the op need it.

sorry for the above waffle.

B

 

[celldweller]

I had the same issue for my CLA 45 AMG that I purchased a few months ago! Unfortunately it was my turbo that had to replaced. It caused my car to have extremely rough idles to the point the car would shut down by itself speeds lower then 25mph. Luckily, I got a deal from a shop and opted out to upgrade to the weistec turbo!

Hope you find the problem, let us know what was the cause?

 

[Faux]

I had no other systems other than when the car was under ‘load’ (overtaking or merging on to a freeway) - hoping you have an inexpensive fix no matter what the problem is.

 

[jmc]

... not feeding the sensor too (does this make sense? - I have no idea about this stuff)

Anyhow all sorted now, I’m sure I still have all the paperwork if you or the op need it.

Wow so a low supply voltage issue ... interesting

Do post the repair order docs - will be great info for forum folks

 

[Faux]

Wow so a low supply voltage issue ... interesting

Do post the repair order docs - will be great info for forum folks

Not sure if this will work jmc or if it hold any relevant info, trying to do all this via my phone drives me up the wall

 

[Faux]

If that is not clear enough, shoot me an email address and I’ll forward it through - the scan app I used puts the file into a PDF

 

[Faux]

 

[jmc]

Oh thats just fine! Great info ... it was wonky sensor

 

[Fergus]

I’ll be sad to this thread go quiet now it’s been resolved. I always chuckle at the thought of ‘violent jerks’ being used by the original poster as some sort of insult to other drivers.

 

[jmc]

Come to think of it ... yeah ... way back at first post it was like a topic on mean drivers who had lead feet

 

[habbyw]

jmc,

they did have trouble diagnosing apparently, luckily a tech was in from Germany and after numerous road tests and a few hours diagnosing they replaced the sensor and my main battery, apparently the voltage was loosing power and not feeding the sensor too (does this make sense? - I have no idea about this stuff)

Anyhow all sorted now, I’m sure I still have all the paperwork if you or the op need it.

sorry for the above waffle.

B

this is something new and I will definitely bring it up to the worksman at the dealership. My only concern is, did you actually get a check engine light warning? Because I haven’t. If you didn’t then it could very likely be the same but if not then I wonder if it’s the same thing or not.

 

[Faux]

this is something new and I will definitely bring it up to the worksman at the dealership. My only concern is, did you actually get a check engine light warning? Because I haven’t. If you didn’t then it could very likely be the same but if not then I wonder if it’s the same thing or not.

No warning lights what so ever, according to the amg tech that was out from Germany he told me it throws ‘soft codes’ (no warning/cel light) - I’m betting you have the same issue as I did -
B

 

[jmc]

“soft codes” may still be stored and reported in the quick test results form
I have noticed from periodic tests there are some error codes here and there despite no CEL indicated ... nothing earth shattering but still those incidents are recorded

 

[habbyw]

Perfect, thank you so much. I honestly hope this is the issue. I'm going to get it looked at by the tech. Will report back with what they say and if it fixed the issue. I'd much rather this than go with the dual clutch replacement that they were suggesting. I never could understand how it would be the dual clutch as this would happen even in Manual mode without shifting any gears...

This is such a relief.

Thanks a bunch!