I have noted a problem with my 140's power plant. I first noticed this occurring around a month and a half ago immediately after starting the car after filling it up at a petrol station. The car fired up without any problems, but it idled very poorly - it felt as though it was not firing on all cylinders. The problem was amplified by putting the transmission into drive - it would hardly accelerate at all. My first thought was crappy fuel. Then again, I had filled up all of my cars at this station on numerous occasions and had never experienced any problems, so ignition-related problems came to mind, especially since it was raining at the time.

At higher rpm the problem seemed less intense and eventually went away after having driven a couple of kilometres. Following this event, everything was fine - the car runs ultra-smoothly and, were it not for the rev counter, one can hardly tell the engine is running at idle.

The problem came back around a week ago - after a car wash. Very poor idle following start up and then running very rough for a couple of minutes. And then everything going back to normal - i.e. running perfectly. Yesterday I noted the problem again (it was a dry, warm day) and have now ascertained the conditions that it occurs under.

The rough running following start up occurs only when the car is started up again after being driven a short distance from cold, so when it is 'half warm', so to speak (the coolant temperature reaches operating level, but the oil does not - i.e. a 3 bar gauge reading at idle). If I start the car up cold, turn it off after a short while and start it up again, it runs perfectly. The same when the engine is turned off after running fully warmed up and then started up again - no problems at all. Similarly, when the car is started up again after half an hour or so, the problem does not occur.
In short: semi-warm engine + shut down + restart = rough running for a couple of minutes.

Any ideas?

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Mateusz
1986 126 500SEL
1986 126 300SE
1992 140 500SE
1996 124 E200T
1999 210 E320T
2017 205 C200T mit Schaltgetriebe!
2010 639 CDI 3.0
2008 204 C180 KOMPRESSOR