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

From your description I would start with a close examination of the distributor caps.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
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1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

The culprit turned out to be the motor's wiring harness - a new harness solved the problem. Distibutor caps were inspected and cleaned but they did not need replacement.

The 119 does get a very slight hiccup once fully warmed (probably once every couple of days), but this would appear to be ignition-related. I will be observing this.

On a side note, judging by the pics in the link below, I am not the only one with the rotting M119 wiring harness problem...

http://users.adelphia.net/~infoage1/complaints_nhtsa_mercedes_wiring_harness_failures_images.html

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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

Oddly enough, MB claims not to know anything about that.

Well, oddly enough, they have lost my loyalty, and the car I just bought last week, is NOT an MB, because I don't appreciate being lied to.

Glad to hear you got your car fixed, Mateuzs! (keep an eye on the ETA a.k.a. throttle body, it can have the same quality wiring, as the harness)

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

It appears as though the harness was not the only reason - yesterday, after a few days of non-usage I fired up the 140 and drove it for a good 10km. The rough idle problem returned and would not go away.

I left the car in the office car park. When I returned in the evening everything was back to normal. I decided to take the car in for further diagnostic testing. Oddly enough, during the entire journey to the MB garage (around 15km), with multiple stops at traffic lights, there was not even the slightest of hiccups.

I will inform of progress when the problem is FINALLY resolved...

__________________
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

The problem has now finally been resolved (or so it would appear). The main reason for the poor running and intermittent lack of power turned out to be the distributor caps and contacts (as indeed suggested initially by MB DOC). The ignition leads were also replaced.

The 140 was unpleasantly heavy on my wallet in September ;-), but it has been returned to an immaculate running order.

__________________
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