Hi everyone,

First of all, I read the forum all the time and did the seach - found many threads with similar problems but none ended up with a resolution. I am hoping that somebody might have found a cure and ended up not posting for some reason.
Problem #1. History: - the 1994 S500 had developed a rough idle (sort of "bumps", more pronounced when A/C is on), lack of power on low end, problems with acceleration - for example, if I accelerate slowly, not bringing RPMs up more than 2000 - it would accelerate fairly smoothly, if I push it harder it feels like I am running on 4 cylinders, the car shakes and rolls and after such event (pushing hard on gas pedal) the idle gets even worse, I would need to turn the car off and on again to reset it.
List of parts replaced:
1. Plugs and wires
2. Caps and rotors
3. AFM
4. Wiring harness
Where do I go from here?

Problem #2. The oil level sensor has developed a leak, quarter sized oil drops are visible on the driveway. It doesn't look trivial to replace it, as I need to get the oil pan removed and it required lifting up the engine. Am I right or wrong?

Thanks in advance.

Sounds to me like your running/idling issues are the result of a vacuum leak. You need to have all of your vacuum lines changed if they haven't been already. They tend to "bake" under the hood, particularly after 10-15 years. Even a small vacuum leak can affect running conditions of the car.

My second thing (which you said you replaced) is your wiring harness. Any 1994 or 1995 car MUST have this done.

Lastly, you need to have a mechanic pull codes from the car. Have them reset it, drive it for a week or two, then have them pull the codes and see what comes up. Often this provides a HUGE clue (if not the offending part or system) as to what is going on. An hour or so of labor ought to be enough to get what you need.

I'm not sure about the M119 engine on the 140 cars, but at least on my 1994 E500 it is a two-piece design, with an aluminum lower part that bolts to a steel upper pan. perhaps the lower pan can be removed to access the sensor? Just a thought.

Cheers,
Gerry

It may well be your ETA (electronic throttle acutator) wiring harness has failed insulation. slit the black plastic cover and check condition if wires inside.

Oil level sensor 'o-ring' seal is easily replaced on the car.

Regarding the oil level sensor, you are going to have to remove the oil pan to replace it. It is a fairly simple job. I would probably suggest replace the sensor instead of just the o-ring do to the sensor tends to leak internal along with the o ring. When installing the sensor, be sure to install it exactly like the old one came out and ensure that the wire will not get rubbed by the crank shaft on the inside of the oil pan.good luck.

Thanks to everyone who replied. I will investigate possible vaccum leaks as well as insulation problems. Will report back on that.

Regarding the sensor, how do I remove the oil pan bolts that are hidden under the frame members (on each side there are couple of such bolts, looks impossible to get to them unless the engine is lifted up a few inches at least).

Check your timing on all 4 cams. Those engines had the typical MB problem in that they would snap the plastic chain rails and skip on one or more cams. Likely either that, the electronic throttle body/M16 actuator, or defective control unit.

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I was warming my M119 500 up (91) and sudden oil pressure drop. 30 seconds later at 0 pressure I'm getting clanging. Stopped engine. Haven't checked oil yet (due to weather in the upper mid-west) but my probability is the oil pump. Thoughts?