W204 C350 hard shifts
Thread Starter
Junior Member
Joined: Sep 2012
Posts: 17
Likes: 0
From: North Bend, WA
2009 Mercedes-Benz C350 Sport
W204 C350 hard shifts
Hey all,
Noob here, picked up a CPO 2009 C350 and of course a few days later I'm noticing some pretty rough shifts. Mainly going into 4th while beginning to let off the accelerator.
My B service is due in 7K, does this have anything to do with it? Thanks for any replies!
Noob here, picked up a CPO 2009 C350 and of course a few days later I'm noticing some pretty rough shifts. Mainly going into 4th while beginning to let off the accelerator.
My B service is due in 7K, does this have anything to do with it? Thanks for any replies!
Super Moderator
Joined: Dec 2006
Posts: 2,403
Likes: 64
From: Camas, WA
2007 C230SS; 2014 ML350 BT
Hey all,
Noob here, picked up a CPO 2009 C350 and of course a few days later I'm noticing some pretty rough shifts. Mainly going into 4th while beginning to let off the accelerator.
My B service is due in 7K, does this have anything to do with it? Thanks for any replies!
Noob here, picked up a CPO 2009 C350 and of course a few days later I'm noticing some pretty rough shifts. Mainly going into 4th while beginning to let off the accelerator.
My B service is due in 7K, does this have anything to do with it? Thanks for any replies!
Senior Member
Joined: Apr 2010
Posts: 410
Likes: 2
From: Orlando FL
2009 C300 4Matic Sport
Welcome...
If CPO, it should be covered by warranty, right?
Having said that, I don't think the mileage is a relevant information, since being a Certified Pre-Owned vehicle, it must not be too high in miles.
I would reset the throttle pedal by following this DIY
https://mbworld.org/forums/c-class-w...eset-w204.html
Let us know if this fixed the problem.
If CPO, it should be covered by warranty, right?
Having said that, I don't think the mileage is a relevant information, since being a Certified Pre-Owned vehicle, it must not be too high in miles.
I would reset the throttle pedal by following this DIY
https://mbworld.org/forums/c-class-w...eset-w204.html
Let us know if this fixed the problem.
MBWorld Fanatic!
Joined: Oct 2010
Posts: 1,128
Likes: 19
From: Acapulco Mexico
2010 C300 Sport
Post #15 of this thread explains why shifts from 3rd to 4th may be "hard":
https://mbworld.org/forums/c-class-w...nsmission.html
https://mbworld.org/forums/c-class-w...nsmission.html
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MBWorld Fanatic!
Joined: Sep 2008
Posts: 1,331
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From: Delaware
2004 Mazda6, 1993 RX7
.... I would reset the throttle pedal by following this DIY: https://mbworld.org/forums/c-class-w...eset-w204.html
Let us know if this fixed the problem.
Let us know if this fixed the problem.
On my 93TT Rx-7, it was still cable driven, but you measured the throttle position voltage signals at Idle and WOT, and then rotated the TPS to get those voltages in spec. Taking another step back, I did the same thing on my "worked" olds 425 ci-in dynamic-88, when I looked down the ports of a holley 780, and made sure there was no tension or excessive looseness in the throttle linkage as pushed the pedal from idle to wide open.
I don't see how, per the last post in your link, that resetting the gas-pedal max and min positions cures all the trans and ecu problems that's claimed.
.
Last edited by kevink2; Sep 23, 2012 at 01:19 PM.
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MBWorld Fanatic!
Joined: Oct 2010
Posts: 1,128
Likes: 19
From: Acapulco Mexico
2010 C300 Sport
@kevink2 - The accelerator reset is hardly a "cure all", although it is a mystery why MB engineers design this vital piece of driver input in a way that it loses its calibration.
Some prefer to do this throttle reset pushing the pedal only half-way down. This improves throttle response as when the pedal is pushed half-way down, the ECU and the TCU receive a signal as though it was floored.
In addition, the 2010 and earlier W204's have a "kickdown switch" at the end of the pedal travel, starting in 2011 this (IMO) vital switch was eliminated.
The ECU should respond instantly to pedal input, not so the TCU which receives data from SEVEN input sources, the throttle and the ECU being two of them. There is a post somewhere with a schematic from a Honk Kong MB training manual (in English) showing all these seven inputs to the TCU.
Some prefer to do this throttle reset pushing the pedal only half-way down. This improves throttle response as when the pedal is pushed half-way down, the ECU and the TCU receive a signal as though it was floored.
In addition, the 2010 and earlier W204's have a "kickdown switch" at the end of the pedal travel, starting in 2011 this (IMO) vital switch was eliminated.
The ECU should respond instantly to pedal input, not so the TCU which receives data from SEVEN input sources, the throttle and the ECU being two of them. There is a post somewhere with a schematic from a Honk Kong MB training manual (in English) showing all these seven inputs to the TCU.
Newbie
Joined: Sep 2024
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w204
Somewhat related to this. there is a backpressure sensor that might be faulty. This creates the sort of fluctuations. I changed mine when changing transmission oil and the fluctuations are gone now. The mechanic had to check with computer to detect this is faulty sensor.
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
OBD SCANNER
Somewhat related to this. there is a backpressure sensor that might be faulty. This creates the sort of fluctuations.
I changed mine when changing transmission oil and the fluctuations are gone now.
The mechanic had to check with computer to detect this is faulty sensor.
I changed mine when changing transmission oil and the fluctuations are gone now.
The mechanic had to check with computer to detect this is faulty sensor.
Failed sensors are flagged by faults.
Its easy to read ECU + TCU modules with a good OBDII scanner along with 40+ modules.
Last edited by CaliBenzDriver; Sep 16, 2024 at 04:57 PM.
