C63s car vibrates/shudders under load
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Joined: May 2016
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C63s
C63s car vibrates/shudders under load
Hello all,
Im looking to see if anyone has experience or can point me in the right direction.
I have a 18 c63s and recently been experiencing an issue where under load at 40ish MPH whether in 4,5, or 6th gear when Im at half throttle the entire car begins to shake and shudder. Originally it would also have a metal rattle noise that sounded like it was coming from the exhaust but its no longer doing that.
I checked all 3 exhaust valves and theyre fine, I did a transmission service with new fluid but did not fix problem.
Checked engine and transmission mount.
im really lost and trying to avoid taking it to dealer,
could this possibly be the torque converter?
Its worse when its in comfort mode
Im looking to see if anyone has experience or can point me in the right direction.
I have a 18 c63s and recently been experiencing an issue where under load at 40ish MPH whether in 4,5, or 6th gear when Im at half throttle the entire car begins to shake and shudder. Originally it would also have a metal rattle noise that sounded like it was coming from the exhaust but its no longer doing that.
I checked all 3 exhaust valves and theyre fine, I did a transmission service with new fluid but did not fix problem.
Checked engine and transmission mount.
im really lost and trying to avoid taking it to dealer,
could this possibly be the torque converter?
Its worse when its in comfort mode
Out Of Control!!
Joined: Nov 2018
Posts: 11,473
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From: San Francisco Bay Area
2019 C63CS
For starters, there's no torque converter in this car. The MCT uses a multiplate startup clutch. Have you scanned it for codes? Otherwise my guess is as good as yours w/o anything to go on.
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Joined: May 2016
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C63s
Ive plugged in Maxi scanner multiple times through out the week with no codes. Next step is trying xentry
It showing no codes has been very frustrating trying to pinpoint the problem. Motor mounts are also fine, it runs completely fine normal driving. Just when in comfort 50% throttle at 2k rpms itll start to shudder
Out Of Control!!
Joined: Nov 2018
Posts: 11,473
Likes: 5,358
From: San Francisco Bay Area
2019 C63CS
Thanks for the info, didn’t know that.
I’ve plugged in Maxi scanner multiple times through out the week with no codes. Next step is trying xentry
It showing no codes has been very frustrating trying to pinpoint the problem. Motor mounts are also fine, it runs completely fine normal driving. Just when in comfort 50% throttle at 2k rpms it’ll start to shudder
I’ve plugged in Maxi scanner multiple times through out the week with no codes. Next step is trying xentry
It showing no codes has been very frustrating trying to pinpoint the problem. Motor mounts are also fine, it runs completely fine normal driving. Just when in comfort 50% throttle at 2k rpms it’ll start to shudder
Last edited by superswiss; Sep 20, 2025 at 07:59 PM.
Thread Starter
Member
Joined: May 2016
Posts: 210
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C63s
Are you in manual mode when this happens? For one thing, at those low rpms, you are essentially lugging the engine. The transmission should be downshifting at those rpms if you give it 50% throttle. If that doesn't happen, then you might have a transmission issue. Does the shudder go away if you downshift before you put load on it? Any issues going WOT all the way to redline?
Not in manual mode and the car downshifts when I rapidly hit the throttle half way. When Im experiencing the issue is when Im easing in on it so the car doesnt think to downshift necessarily.
On WOT in sport doesnt have any problems but I notice top end power is sluggish and feel like turbos arent performing. Almost like NA power.
After doing some reading Ive learned that older version coil packs would have symptoms exactly like what Im experiencing. Im going to look into purchasing updated packs and seeing if that resolves.
(Below is what is said about old coils)
thanks
- Misfire Under Load
- Smooth at idle and light throttle.
- Shaking/vibration in higher gears at low RPM when boost builds.
- Feels like power cutting in and out.
- Loss of Top-End Power
- Engine feels flat past ~45k RPM.
- Boost gauge shows pressure, but car doesnt accelerate as hard (because cylinders arent firing cleanly)
- Clunk/Shake Around 23k RPM
- Especially noticeable in 5th7th gear, half throttle.
- Feels like drivetrain vibration but is actually misfiring
Out Of Control!!
Joined: Nov 2018
Posts: 11,473
Likes: 5,358
From: San Francisco Bay Area
2019 C63CS
Not in manual mode and the car downshifts when I rapidly hit the throttle half way. When I’m experiencing the issue is when I’m easing in on it so the car doesn’t think to downshift necessarily.
On WOT in sport doesn’t have any problems but I notice top end power is sluggish and feel like turbos aren’t performing. Almost like NA power.
After doing some reading I’ve learned that older version coil packs would have symptoms exactly like what I’m experiencing. I’m going to look into purchasing updated packs and seeing if that resolves.
(Below is what is said about old coils)
thanks
On WOT in sport doesn’t have any problems but I notice top end power is sluggish and feel like turbos aren’t performing. Almost like NA power.
After doing some reading I’ve learned that older version coil packs would have symptoms exactly like what I’m experiencing. I’m going to look into purchasing updated packs and seeing if that resolves.
(Below is what is said about old coils)
thanks
- Misfire Under Load
- Smooth at idle and light throttle.
- Shaking/vibration in higher gears at low RPM when boost builds.
- Feels like “power cutting in and out.
- Loss of Top-End Power
- Engine feels flat past ~4–5k RPM.
- Boost gauge shows pressure, but car doesn’t accelerate as hard (because cylinders aren’t firing cleanly)
- Clunk/Shake Around 2–3k RPM
- Especially noticeable in 5th–7th gear, half throttle.
- Feels like drivetrain vibration but is actually misfiring
Has this car been properly maintained? What's the mileage? Spark plugs changed at every 50k or 5 years whichever comes first? Is it tuned? Fouled spark plugs is common on tuned cars for example.
Last edited by superswiss; Sep 20, 2025 at 08:21 PM.
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11 E550, 16 AMG GTS, 13 S550
sounds like flame propagation issues, its probably spark
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