I'm at my wits end with this...

I have a 2004 C230K with 45,000 KM

When the engine is cold (i.e the vehicle has not been started for several hours, regardless of ambient temperature) it starts absolutely fine and idles magnificently (it always has) however the second I shift into gear (reverse OR drive, comfort OR sport, manual OR automatic, doesn't matter) there is a very sluggish feeling and the car will abruptly stall if the brake is kept depressed. Most times if you were to shift into gear and immediately release the brake the sluggishness is still apparent and it sounds and feels like it's going to stall but won't if you let it roll and then shift to neutral right away, you can then shift to drive, again as long as you release the brake immediately, after doing so for approximately the next 15 minutes of driving any complete stops will result in a violent vibration throughout the vehicle and again it feels like it wants to stall. As soon as the engine has warmed up completely (water temp consistently at 80 degrees centigrade) the issue goes away completely, it shifts and drives like a dream. You can then leave the vehicle sitting in any temperature for an hour or three and go to drive it, still no problem. It's when the vehicle sits for an extended period, typically overnight, but likely around 5-6 hours minimum.

The issue does not occur whatsoever when in park or neutral.

So I brought it to the dealer and from what the service advisor told me, and what is shown on the invoice, the technician(s) checked the car's computer and claims that it was displaying trouble codes in relation to the misfiring of cylinder 2, a spark plug was removed and cleaned. Coils #2 and #3 were swapped, the engine control software was also updated. Total $204, warranty timed out :-(

When I heard this I was pretty confused. While I'm no Mercedes-Benz mechanic, I do have a very good idea of how cars are put together and what makes them run, the "resolution" just did not sound right. If there was a misfire, why would the engine idle just fine? Would performance not be drastically decreased on a 4 cylinder engine if one of them was misfiring? Why would this not produce a check engine light? It sounds logical to me that because the issue goes away completely when the engine is warm that something needs to be re-calibrated, or possibly replaced.

Before driving away I checked the water temperature and it was at 60 degrees C and the outside temperature was -25C. This means that the vehicle was recently driven or warmed up, so I knew immediately that the issue would not be present, which it was not. I knew I would have to park it again overnight to see if the issue returned in the morning, which it did, exactly the same as before.

I'm leaning towards the torque convertor, but who knows... Would really appreciate some assistance on this!!

Thanks in advance!

 

Can't fault your description wrt "stalling".

So no trans codes have been set? In which case it looks like a mechanical rather than an electrical problem.

Trans oil correct type / level etc?

Could be the TC stator clutch as you suggest.

I would have favoured a valve block / electronic control system problem rather than TC since you state all is fine once warm. However the TC stator design behaves differently at high speed vs low speed so it would fit.

.....................
WRT engine misfire code.

Cleaned the plug? Why? Why not change it or all. Strange. Most plug failures do not respond to "cleaning"

OK swapped coil packs. What effect did this have. Move problem from 2 to 3 or vice versa? If not then I would expect plug to be changed or other work done. Injector etc.

Did they changeor swap the accompanying lead?

Misfire can be intermittent. Low (engine) speed or high speed

Why update the ECU software for this sort of problem? What sort of problem is the updated software supposed to resolve? Suspicious.

Charge seems reasonable for work carried out but what was the outcome. Is that fault now cleared? Is a misfire code still present?

......................

Sorry can't add much more.

Stuart

 

Hey Stuart thanks so much for the prompt reply, could you explain what WRT means and what a transcode is, how it's set etc.?

Also do you think it could have anything to do with the IAC valve? I would like to try spraying a shot or two of carb cleaner and a dash of WD40 on it to see if that clears things up but I have no idea where it is, my best guess would be near the throttle body, any idea?

 

Hi,

WRT = with respect to

Trans code is an OBDII diagnostic code for the transmission. Basically unique numbers for fthe transmission rather than the engine. Same connector to car, same scanner and process.

OK?

Stuart