I've always been curious as to how these engines are supposed to idle. With new engine and transmission mounts installed, I can barely feel the car shudder, but I can clearly see the engine shaking around in the engine bay. Is this normal?

Did you do the engine shocks too? Don't really know if that makes a difference, but nobody ever replaces them.......

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-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Going to do some searching, didn't know about those... and sorry for the thread jack!

My 91 300SE (M103) started misfiring just recently....turned out to be the plugs were worn out...I replaced all 6 with new Champion brand standard copper core plugs set at (.032) gap...now its running perfectly again...I've been told that Bosch were the idea plugs for M103.

The W201 and W124 engine shocks for the M103 and 104 engines are integrated into the motor mount. The W126 engine shocks are separate.

In my experience, M103 engines can idle a bit lopey without a load but are very smooth with some load (A/C, in gear). As MB stated in the owner's manual for my 300TE, this is "state of the art" for KE injection systems. However, you may want to test the O2 sensor to ensure that it responds as intended. Mark

Mine has the "spluttery" idle when in gear, but it dont have the hard starting issue... hot or cold, it starts instantly.

I am going to try plugs and hope.

o2 sensor may also be part of it. My "check engine" light will illuminate after the engine has been running for 2 minutes, then it will go off 2 minutes later and dont come on again- until the next time I turn it off and start again.

one addition that made a dramatic decrease in underhood temp and the hot engine idle on my 300se /90 was the installation of a heat insulation wrap on the exhaust manifolds down to the first joints.
the temp stays at around 80 "C instead of 100C during the very hot months. A/C also is super cool due to lower temp. As the underhood temp is low at switch off the injectors should stay cleaner (lower heat soak).

mak

I had taken the very slight and occasional tremors as part of the 103 running .
Replacing all the ignition consumables had no effect , but now engine is running perfectly smooth and steady .How?
The engine had a slight belt chirp when starting from cold, replacing the bad tensioner, belt and the bent adjuster rectified the noise.While the belt was out i serviced the alternator ,cleaned the commutator and replaced the voltage regulator as the bushes were down to a few mm.
The voltage now is 14.1V as compared to 13.6 V earlier on and dipping under 13V with the blower wiper and headlight load on.
I believe the charging system must be perfect too to achieve good running when all the other parameters are correct.
mak

new voltage regulator... our erratic idle went away.

Interesting!

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1991 300E - 212K and rising fast...

I know. Someone told me that could be the erratic idle problem. I guess it was where the car was fluctuating the volts causing it... guess so. I am not complaining.

I have been chasing this issue with my 88 300E for a while now. You kind of learn to live with it.
No matter how many times I have gone thru the ignition it has never helped. My next thing to look at will be the fuel accumulator and injector seals,and have a look at the voltage. Thanx guys this post has restimulated my interest in the old 300E. John....................................................

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88 W124 3.0
96 R129 119eng
06 ML350
98 ML320 sold
02 CLK55 amg