My 1994 S320L doesn't get smooth idling in GEAR ONLY and happens much more frequently at night with cold weather outside .Otherwise,it is perfectly fine.When the car is idling roughly in gear, I notice the pressure gauge is fluctuating and the engine wants to go....and go...and go.Last night I noticed the transparent tube (Vaccum lines?) was very hardened.Is that supposed to be hard or flexible.Does airleakage cause that problem?? (I sent the car to an authorised Mercedes workshop and they told me the car is fine with the computer diagnosis.)This problem has annoyed me enough and it just makes me crazy!!Any help is appreciated,please!!

An intake vacuum leak is the usual cause for rough idling. I assume the plug wires and plugs are in good shape, and your engine compression is good.

If your dealer cannot solve your problem, request to see the regional tech rep for solution.

Have you check your engine mounts?????

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MB STARS Master Guild Technician,12 years MB tech
5 years independent shop owner

I had the same problem, and it was my engine mounts ;-)

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Brian Drought
1991 300CE
http://www.users.globalnet.co.uk/~drought/
ICQ: 2180069

Brian,
Did you have the exact problem ??- I mean the idling is not rough but fluctuating in gear and happens in cold weather(at night,under 16c).Does it deal anything like the air/temp. sensor(the first sensor from the air box)??
From Davis Lo

Davis:
It is possible that a small manifold leak will cause a uneven idling condition. Due to fact that you are not in the US I do not know what fuel system/diag. version your car has. The tech should be able to monitor the mixture and look at the long term adaption numbers and see if the engine is running lean.
Good Luck.

I thought you meant a vibration coming thru...

As far as lumpy idle goes, mine was the temp sensor contact were dirty. (I think... whatever it was went away....almost)

Theres a slight lumpiness still, but cant feel it with the new engine mounts anyway ;-)


Brian



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Brian Drought
1991 300CE
http://www.users.globalnet.co.uk/~drought/
ICQ: 2180069

OK!I almost get it!!I find that if I drive the car at night WITH the DEFROSTER ON for the rear window , that funny stalling would disappear definitly.I suspect that there is something wrong with the electrical system.Has anyone experience that before??Anyhelp is appreciated,please.
S.O.S. from
Davis Lo
1994 S320L

Have your charging system checked for overcharging. I have seen a few cars with traction control systems do strange things when the system voltage exceds 17.5v. The use of the lights and rear defroster would help to keep the voltage down.
Good Luck