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W204 C350 hard shifts

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Old 09-18-2012, 06:38 PM
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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!
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Old 09-18-2012, 06:47 PM
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Originally Posted by rjmcc01 View Post
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!
What it the current mileage on the car?
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Old 09-18-2012, 10:06 PM
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Ask the dealer to check on the Star, if the 7G transmission TCU has had the 2010 TCU software update? Will probably solve this problem.

Got mine done without cost.
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Old 09-18-2012, 10:08 PM
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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.
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Old 09-20-2012, 02:45 PM
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33K, thanks for all of the replies, I'll get it in and ask for the software update and a throttle reset at the same time, thanks again.
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Old 09-22-2012, 10:35 PM
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subscribing for future reference. im also new here and mine does not shift as smooth as when i first test drove my car either.
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Old 09-23-2012, 07:45 AM
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Post #15 of this thread explains why shifts from 3rd to 4th may be "hard":

https://mbworld.org/forums/c-class-w...nsmission.html
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Old 09-23-2012, 01:16 PM
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Originally Posted by ggms16 View Post
.... 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.
AFAIK, that gas pedal reset just recalibrates the idle and wide-open pedal positions.

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; 09-23-2012 at 01:19 PM.
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Old 09-23-2012, 01:57 PM
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@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.
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