Wargen

When i start up my C200 kompressor and the temperature is around or below 0 degrees celsius it runs very rough. The engine sounds very rough and the supercharger whines like a mopar, the first gear changes is also very rough compared to when its warm.

All cars runs a bit rough and sounds different when its really cold but the C200 runs very rough and ive only experiensed about 0 degrees celsius with the merc so far, which shouldent be a big deal. Not that its a very big issue but i drive most short distances where the car barely gets warm, and its annoys me that it feels like crap for those 5 minute drives in winter.

You who live in cold climate, have you experiensed the same thing? That its running super rough when its cold compared to other cars?

hazee

It sounds strange even if its not zero degrees. So I start the vehicle and wait for 5 minutes in parking. The engine gets warm and then neither its noisy nor rough.

Its a good practice to warm up your car engine before you start driving. Better health, long lasting.

C300Sport

Don't be so sure. It is actually better to allow the car to idle down, maybe for 10-30 secs and then to start driving "gently". This will save you time and gas, reduce emmisions and reduce the amount of deposits left in the engine from cold start idling.

coolvi

Since day one, the engine sounds rough (in terms of relatively higher and unstable revolution speeds, which is normal) in my C300 at startup. I always let the engine rev. down to about 600-700rpm which usually takes about half a minute (the first dramatic spin down from the engine I can hear) before taking off. I did the same one day last week when it was parked in -25ºC (due to my bad planning: parkade at school, underground pass isn't active until Jan.). Well, fortunately, I didn't feel significantly different from starting it up at +25.

patrickkc

oh, your in alberta you guys got hit with the deep freeze last week... glad the car suvived through that!

Petje

Have the same here, i'm always starting my car and wait till it's idle down... so after about 30sec/1 min i drive. Not directly.

But the engine/supercharger sounds very rough when its cold...

Glyn M Ruck

+1

This seems to be a characteristic of the M271 engine in very cold conditions. I drove one in the cold in Harbin in NE China last year. It was damn cold - minus plenty & this car had no block heater fitted. Low mileage vehicle.

It was rough as a bear's **** at start up.

All these cars go onto high idle to warm up the Cat quickly to reduce emissions. This aggravates rough gear changing when cold even with the new Benz synthetic transmission fluid.

This car in China was perfect once warm. I speculate that Benz has become so paranoid about emissions that they run the things too lean at cold temp start up.

Your only options are really to make sure that the engine temp sensor that feeds the ECU is OK & you have the winter thermostat fitted. I'm pretty sure you do.

amowolves

sorry to bring up an old thread, but i was going to ask the same question as the op.

My cars coming to the end of the warrantee and though its been great the one thing that ive noticed esp now as the weathers colder is how rough the c200 is on cold start! almost diesel sounding! it seems to get smooth once the engine is warm but i too only really use the car for short journeys so by the time it does, it time to park it up again.....think its an excuse to go for a long drive this weekend! lol

just thought i'd do a search incase it was a fault as ive even had a couple of people ask me if its a diesel! doh.

Glyn M Ruck

As long as the car has no vacuum pipe leaks etc it should be OK. There was a $12 hose recall on the M271 - make sure yours has been done by checking your VIN with the dealer.

The M271 is a little like a lawnmower until warm.

amowolves

cheers Glyn will do...was there any other recalls you know of? i did ask my dealer abotu recalls as it went in for its first MOT test last week and he didn't mention any.

Glyn M Ruck

The only other things you have to watch on the M271 engine is oil leaking from the 2 cam sensors on the front of the engine into the wiring harness. Unplug & look for oil.

EDIT Forum is dropping pictures again - here

Sentosa

Hey Glynn

I hope you haven't been that close to a bear *** to know how rough it is.

Glyn M Ruck

amowolves

cheers thanks, will take a look on the weekend.

Glyn M Ruck

If you find oil make them change the sensors & clean the harness - then fit pigtales. Oil in the harness leads to ECU problems and O2 sensors misreading fuel trim - usually drains down to the O2 sensors first. This has been far less of a problem on the W204. QC on the sensors seems to have improved.

Sentosa

Glyn, on the W204, if I had this problem would I be able to smell oil just prior to and during start up?

Glyn M Ruck

Unlikely - Only after start up if it had drenched the O2 sensors on the exhaust.

Sentosa

Thanks for that. I just have this strange smell like hot or burnt oil when I jump in to start it after it has been standing overnite.

amowolves

thanks for the info and pics Glyn, much appreciated.