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Discussion Starter · #1 ·
I've got a 2008 451 Pure. So, I recently replaced my clutch actuator after the one that was on the car when I bought it failed (worm gear broke). I got the new part online and it looked slightly different, nicer milled surface instead of a sort of rough cast on the casing compared to my original actuator. This may or may not be related to the problem.

Since I installed it, I've had trouble with the car basically dumping the clutch when starting to move, whether into 1st or Reverse. It sometimes makes a bang sound and moves far faster than it should without me pressing the gas pedal. Often when I start moving it slams the clutch, retracts it for a moment, and then clutches in again. It also lurches downshifting from 2nd to 1st. I recall it occasionally doing this before, though it seems to be worse now.

I've tried adjusting the position of the clutch actuator and it improved the situation for a couple days, until once it failed to clutch in and I rolled back when starting on a hill. After that it seems like it's overcompensating and slamming the clutch even harder.

Has anyone ever experienced this problem before? Is it probably the fault of the actuator itself, or maybe a sensor or the shifter motors? Nothing I can do in my driving style EG holding the brake to start, getting on the gas very gently, seems to help. It also shifts totally fine when it's moving, the problem is pretty much exclusive to starting to move from a standstill or downshifting into 1st. Is there a way to force a fresh transmission teach-in? I know you can teach the transmission when the 3 bars come up, but that only seems to happen when the car decides the transmission is bad enough, which it hasn't yet.
 

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Discussion Starter · #3 ·
It looks just like the one in that picture, I assume making it the Sachs version. It came with all official labeling (for Smart GmbH IIRC) This car was a 2008 preorder for the united states so I don't know if that would mean the originally installed actuator would be different. Frustratingly the issue has also been somewhat intermittent, on some days it would be fine (until recently) but I could never get it to go away consistently. I did pay a lot less than $542 for mine, but your picture looks quite identical to the new one I bought (and still slightly different from the old one, unless I'm fooling myself and it was just a lot of corrosion).

Has anyone else encountered this particular clutch dumping issue from a knockoff clutch actuator before, or is anything else known to cause it? I'd hate to buy a redundant $500 part and find that it's not the source of the issue.
 

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Discussion Starter · #6 ·
Some weeks on, I've had mixed results fixing this. What eventually happened was that it got much worse until the engine stalled out a couple times in a row. I thought I was going to have to get a tow but it started working again, and it was engaging the clutch late instead of early. I limped the car home and and re-adjusted the actuator to a more normal position and it was driving great, for a couple days. Later it started slamming again, which I think was connected to manually downshifting into 1st.

At that point, I tried the throttle body reset a couple times, which didn't seem to work at first but it got to working properly later. About a week later it started slamming again (also immediately after downshifting into 1st) and that time, a throttle body reset got immediate results, so there's definitely something to it.

Now, that went fine for another week or so until it started doing it again, and I'm pretty sure I didn't downshift into 1st too early but maybe I did without realizing or something, it seems like it often happens after I slow down hard from a freeway exit. I've not been able to get the throttle body reset to work, or not to perfect results anyway, but maybe I'm doing it wrong. It seems to be a finicky procedure with how long exactly you need to wait.

I also had tried disconnecting my batter earlier (sometimes overnight) to no effect.

I think there's some underlying cause that makes the car so prone to "calibrating" itself so that it's incapable of starting smoothly or creeping. That cause might be a very worn clutch, if it's detecting clutch slippage it may be overcompensating. But, the throttle body reset procedure has at least been a useful band-aid so far.
 

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Some weeks on, I've had mixed results fixing this. What eventually happened was that it got much worse until the engine stalled out a couple times in a row. I thought I was going to have to get a tow but it started working again, and it was engaging the clutch late instead of early. I limped the car home and and re-adjusted the actuator to a more normal position and it was driving great, for a couple days. Later it started slamming again, which I think was connected to manually downshifting into 1st.

At that point, I tried the throttle body reset a couple times, which didn't seem to work at first but it got to working properly later. About a week later it started slamming again (also immediately after downshifting into 1st) and that time, a throttle body reset got immediate results, so there's definitely something to it.

Now, that went fine for another week or so until it started doing it again, and I'm pretty sure I didn't downshift into 1st too early but maybe I did without realizing or something, it seems like it often happens after I slow down hard from a freeway exit. I've not been able to get the throttle body reset to work, or not to perfect results anyway, but maybe I'm doing it wrong. It seems to be a finicky procedure with how long exactly you need to wait.

I also had tried disconnecting my batter earlier (sometimes overnight) to no effect.

I think there's some underlying cause that makes the car so prone to "calibrating" itself so that it's incapable of starting smoothly or creeping. That cause might be a very worn clutch, if it's detecting clutch slippage it may be overcompensating. But, the throttle body reset procedure has at least been a useful band-aid so far.
My problem was always slamming the clutch and all my rests only lasted a week or so, I ended up replacing the actuator myself and everything has been fine since. I paid $400 incl shipping for the actuator, so it was an expensive gamble, but it paid off. You might find a lower cost one, but I recommend staying away from used (unless it is VERY low cost) because it might have the same problem...
 

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My problem was always slamming the clutch and all my rests only lasted a week or so, I ended up replacing the actuator myself and everything has been fine since. I paid $400 incl shipping for the actuator, so it was an expensive gamble, but it paid off. You might find a lower cost one, but I recommend staying away from used (unless it is VERY low cost) because it might have the same problem...
By the way, I had decided that my replacement was going to be a Sachs unit since they are an OEM for Mercedes. Other brands are cheaper but since I was gambeling on the cure I did not want to gamble on the brand.
 

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Why the heavy manual down shifting to first. Once the software that adapts to your driving sees that heavy rev spike it makes that extreme adjustment. Reading articles on MB software seems to indicate the last 40 shifts are what the software uses to "adjust to your driving style" that is why you can drive more "normal" and in not to long have that spike fall off the average and return to a softer clutch action. What the reset does is wipe that last forty data info out to a factory default. The same happens with over reving take offs for on ramps and standing still launches. 1st to second and 2nd to 3rd shifts are the issues. I can not think of any reason I would down shift to 1st on purpose with the car in motion. I am very conscious to not over rev in 1st and 2nd as I hate, Hate, Hate the clutch slamming you are talking about and when I make that mistake on an on ramp launch only to end up in stop and go traffic. I will pull off to the side of the road and reset the car before I let it bang like that. But now that you have confirmed to yourself that you can cause that slamming 100 percent anytime you want to, just by over reving in 1st and 2nd gear. Make your new commitment to stop doing that. You are Annoying your Smart and probably Abusing it. And when you are committed to Annoying and or Abusing your Smart....... It ultimately will quit on you.
 
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