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.

__________________
Don't ask me, I'm a shop-owner by default

As you will read below, removing the oil pan on a M119 in a W140 is not an easy task. There may be a "trick" on ways to avoid certain steps below, but this is documented method for removing the oil pan. (Please see thumb nail of the pic below for more details.)

Hope this helps!
Russell


Raise hood to vertical position.
Disconnect ground cable at battery.
Remove air scoops. See: Powertrain Management\Fuel Delivery and Air Induction
Remove viscous fan clutch (1). See: Cooling System\Fan Clutch
Remove tensioning device (24) for poly V-belt. See: Drive Belt Tensioner\Service and Repair
Unbolt TDC sensor.
Unbolt dipstick guide tube (4) at air pump bracket.
Remove bottom engine compartment panels.
Drain engine oil.
Remove bracket (19).
Remove belt pulley (12) and vibration damper (13). See: Harmonic Balancer - Crankshaft Pulley\Service and Repair
Remove carrier with guide pulley.
Installation Note : Pay attention to fixing sleeves. Tightening torque 21 Nm .



Detach A/C compressor (22) with lines/wiring connected.
Installation Note : Pay attention to fixing sleeves. Tightening torque 21 Nm .



Secure A/C compressor (22) to the side in engine compartment.
Remove carrier (22a) of A/C compressor or guide pulley.
Installation Note : Tighten bolts to: 21 Nm.



Remove alternator (3) upward.
Remove bracket (2) of alternator.
Installation Note : Tighten bolts to: 21 Nm.



Unbolt Dipstick guide tube (4) at oil pan (20).
Installation Note : Replace seal (4a) according to condition.

Unbolt both engine mounts (9) from below.
Installation Note : Tighten bolts to: 25 Nm.



Remove front axle (28) springs (24) of front axle (28). See Steering and Suspension.
Unbolt shock absorber (27) at top.
Install engine supporting bar: special tool 140 589 01 61 00.
Remove shield (26) of steering coupling (25).
Unbolt and detach steering coupling (25), refer to Steering and Suspension.
Support front axle (28) with vehicle jack attachment: support using special tool 140 589 00 62 00.
Remove rear covers of bolts (22) of front axle.
Unscrew microincapsulated bolts (22) of front axle (28). Refer to Steering and Suspension.
NOTE:


Use 6-point wrench insert, WAF 21, for this operation.
Before installing re-tap thread in body with M14 x 1.5 thread tap (clean).
Replace Microincapsulated bolts (22).
Lower front axle (28) sufficiently until oil pan (22) can be removed.
CAUTION : When lowering, pay attention to hydraulic oil lines of brake and steering gear.

Unbolt oil lines of automatic transmission (23) and air-to-oil cooler at oil pan (20).
Disconnect electric cable of knock sensors at bracket of power steering pump at rear.
Unscrew bolts of oil pan.
NOTE: Pay attention to hexagon socket bolts (18) at rear of oil pan (20).



Remove oil pan (20): take off down and to the front.
Installation Note : The rear contact surface of the oil pan (20) has to be aligned to the rear contact surface of the crankcase (arrows). If the oil pan (20) is not aligned to the crankcase, this can result in noise and vibration problems.



Replace gasket (20a).
Apply sealant 002 989 45 20 (Omnivisc) in rear area of oil pan and on crankcase.
Run engine and check for leaks.
Install in reverse order. Observe all notes, installation notes and tightening specifications.
Tightening Torques:

Attached Thumbnails

 

To replace the low oil level sender you will not need to do much more than loosen the engine mounts, lift the engine slightly, then place a 2x4 under the front edge of the upper (aluminum) part of the pan and the sub-frame. Lower engine so it rests on the 2x4 while you R&R the lower oil pan. Use a 5mm allen with a swivel (1/4 5mm swivel socket by Snap-on works best) to remove the forward section bolts, a regular allen will do the rest. Less than 3 hours on your back, under 2 hours on the rack…………..at a casual pace.
I apply a little “Ultra Black” sealant to the inner part of the sender, you’ll want to clean the block side with brake-kleen prior to installing the sender.

The lack of power can be a few different things, you will need to have the vehicle scanned for codes. Look for DTC’s in LH-SFI, DM, EA or ISC/CC, and DI. The engine harness may be a must, the actuator may also be a must just look at the insulation and it will reveal itself. This would be a good place to start before any of us could offer you meaningful suggestions.

solve your power accel problem, take the car to a muffler shop and have the cats/mufflers checked; they may be blocked.

Saw a E500 that had the same problem, although it idled fine but had no power when you wanted to make it move. The cats were blocked.

__________________
Regards . . . . JimF
-------------------
'94 S500 Cpe

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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?

Is this spec repair from the manual for r129 M119? That $400.00 ( in 2004 though) sure might have been worth it.