Hello all, new here and new to Mercedes vehicles as well.

I just bought my first, a 2011 E350 4Matic with 180k. It was well taken care of and is exquisitely clean for its age and milage. I've had it for a few days and love it, however I am noticing a few issues that have me worried.


Background;

The previous owner took great care of the car, replacing any failing parts and doing maintenance on time and with quality OEM parts. As part of this, he told me he changed the transmission fluid as well as the filter, and transmission pan as it was rusty around the drain port. He told me he "made sure to use the correct fluid" when he did the change but did not get into any further details about it. I do not know if he cleaned the solenoids, or drained the torque converter as part of the service. He also replaced the throttle body gasket and the plastic elbow. He's done a lot of other various things, new plugs/coils, new oil filter housing, its lowered on springs and is currently on winter tires too. I personally know the seller, and probably wouldn't have bought a Mercedes from anyone else being I know how he takes care of his vehicles.


Issues;

The car drives well, the suspension is a bit stiff since its lowered and all but I don't mind that. The snow tires give some vibrations as well which is expected.

However, between 30 and 40mph, the tachometer jumps around a bit, at first I figured it was a faulty gauge but you can definitely feel it as the engine surges up and down, its probably no more than 100-200rpm. From my knowledge, stuff like this is caused by vacuum leaks and being the previous owner did the gasket at the throttle body it was my first suspect. However, if I accelerate past 40mph, the surging of the RPM's stops, but then I'll get what I can only describe as a "rumble" from under the car. Similar to what it feels like to drive over rumble strips on the highway. I've done a lot of reading and googling on various forums/youtube/facebook and I'm under the impression this could be a torque converter issue. The rumble doesn't happen all the time, and happens more frequently when the engine is cold.

From what I gather, the previous owner either didn't use the correct fluid, or one of the clutches in the TC is on its way out/slipping under acceleration. Either way I'm not happy about this and would like to figure out how to fix it.


Steps taken;

So far, I've done the TCM reset procedure of holding the gas pedal down for 30 seconds while the key in sin the 2nd position. Slight improvement but could be a placebo effect.

Asked the previous owner about this, he said he never noticed it.

RPM surge/rumble happens in both E and S mode, shifting manually doesn't change anything either.

Rumble gets better as engine warms up, RPM surge is always there though, if I accelerate like a granny going to church RPMs remain steady usually.


I've seen this issue pop up here before and would love more insight on what I may be dealing with.

 

You are right about not ignoring early service clues.

- A - The Rpm wander is not unusual. I believe it is caused by unstable fuel pressure.

- B - The ramble is from a component of your powertrain:

1. Xfer case oil
2. Front/Rear Diff oil
3. Prop shaft Center bearing
4. Engine/tranny mounts too low

722.9 tranny itself is fairly robust unless you're racing with your shadow then it needs shorter ATF service intervals.

 

I'm wondering if tackling the RPM wandering around is the first step here. I just came across another thread discussing similar issues and trying to point it to a fuel pressure issue.
I decoded the vin. I have a M272 engine with the 722.9 trans. Is there a good scanner you could recommend? I only have basic OBDII scanners.

 

the scanner a lot of us enjoy is the Launch MB creader Elite priced around $130.... a bargain considering its excellent MB modules coverage.

There are many other more expensive or lesser qualities... new ones come out every month - Some Bluetooth dongle units could be appealing (not ELM327).... dono.

Launch produces a complete fault report of the whole car with meaningful descriptions instead of couple module codes.

 

A small update;
When the engine is fully up to temperature and I have been driving for at least 20 minutes, if I switch into Sport mode from Economy, everything suddenly gets better. Smooth (but noticeably harder) shifts, no shuddering, the RPMs still bounce around a bit but seemingly not as much.
Surely this must be a clue as to what's going on right? Surely the issue must lie within the "Economy mode" circuit of the transmission?

 

I have a coworker bringing his Autel scanner in tomorrow so I'll be able to get the codes off the transmission. Hopefully it'll point me in the right direction as to what may be going on.

 

There are multiple reasons the tranny uses the wrong gear ratio in E- mode - It's all about the engine poor throttle control. Nothing wrong with great tranny itself.

In City drive with "S-Mode"
In Hwy drive with "E-Mode"

In the city "E-mode" over works the TC lock-up clutch that leads to high heat unnecessary tranny failure repairs.

 

Today's update:

I was able to scan the car with my coworkers Autel scanner. No present or stored codes relating to the transmission, however, looking at the live data its seems that the torque converter never fully locks, and flares between 3rd and 4th gear.
I'm not sure where to go from here, my mind tells me this may be a fluid, contamination, or pressure issue. Maybe a gummed up solenoid? Low fluid? I don't have an easy way of checking fluid level right now but its one of the first things I want to do.

 

there's no easy way to check ATF level short of doing tranny service....

You can simply look for evidence of leaks... that will allow you to guess correctly about missing ATF.

Tranny is a really closed circuit. No active leak means 95% chance level's right!

So you know: this 722.9 reportedly has "multiple levels of TC clutch locking" to make it run smoother.

If its not shifting well.... valve body refurb may be coming your way but then someone needs to troubleshoot clutch vs. solenoids... an expert's job!

 

Based on what you have said it seems to me you have TC locking issue going on.

The RPM surging should make the car speed surging with it if the gear does not change. With the scanner you are able to see what gear is ON so if the gear does not change AND the RPM keeps surging the TC lock must not be holding as if it is holding and the gear does not change the car speed will definitely surge with the RPM that you would also feel even if the RPM surge is only a couple hundred RPM. And I do not read in your posts that you feel the car surging, just the RPM.

This would be a TC issue or it could also be a transmission hydraulic pump issue.

Of your symptoms the surging happening at certain speed area can be due to engine torque reaching the peak value at that speed.

The “rumbling” under car can be the TC lock doing “stick-slip” under too much torque for it to hold.

For the fluid level check you can take the drain plug off. There is a riser tube inside that sets the fluid level. You can add fluid with a skinny tube but be careful not to force that riser tube loose as that would make the whole fluid to drain. Or you can buy the special filling connector for it.

After adding fluid let it drain to the level the riser tube sets and this all needs to be done with the car perfectly level, of course.