Howdy! I have a 2012 E350 wagon (S212) M276 motor w/ an engine hesitation. It primarily occurs on a slight uphill gradient when the engine is at a sustained throttle point. I can usually trigger it to occur at highway speeds (around 70mph, 2000 rpm). It presents w/ a light hesitation / minute drop in engine RPM that seems cyclical. Hesitate, then regain rpm, then hesitate. Its very mild, almost as if a gust of wind hits the car in 1 second pulses. It will occassionally "misfire" & the hesitatiion will be pronounced. Warmer weather seems to present this problem more so. If I change the throttle even minutely up or down, the engine will smooth out & the hesitaion / misfire goes away immeadiately. I changed the spark plugs, coils, cam position sensors, cam position solenoid magnets, w/ OEM parts with no change in this symptom. I did note oil in the throttle body, duct work & scant oil in the filter airbox. I believe this oil accumulation is an established issue w/ the PCV system? Ill clean noted oil & it slowly returns in 5K miles. Anyways, its where my trouble shooting is focused after ruling out the previous repairs / maintinance. I was thinking MAF sensor is getting contaminated / in need of clean? This symptom does not occur driving around town or any other situation. Engine drives great otherwise, always run premium fuel. I have no check engine light & the only code my OBD reader (foxwell) shows is a lingering P050C (cold start engine coolant temp performance). It will trigger the aux fan to run all the time & display a dash outside temp (over 100 degrees on a 69F day).My shop changed the ECT (engine coolant temp) sensor at great labor cost to no avail. I clear the code when it coincides w/ aux fan running to stop fan. Not sure if this code ties into my engine hesitation, but thought I'd mention it. Im stumped & my trusted mechanic can't seem to get the symptom to occur on test drive / code reader. Appreciate the input & help on this issue! Thanks!!

 

You have covered a lot of items to fix your M276-NA mild hesitations that is running well.


The throttle hesitations at 70mph you are sensing is from a lean fuel maps. Many items can contribute to that.
This is a normal ECU response. It is leaning fuel from partial combustions to preserve cats.
You just need to restore the GDI engine ability to burn well.


What is current mileage ??
What sort of driving : city, Hwy commute, track racing ?

This M276 NA engine does not use a MAF but a single MAP only. MB has this sensor mounted sideway such that it accumulates some of the intake oil inside.
Take 5mn to empty the oil out of sensor and clean it gently with spray. Let it air dry, don't use shop air on the delicate pressure sensor. Reinstall clear the fault.

Next considerations may be:

1. ignition tune-up: plugs + boots: 50kMi?
2. fuel pressures (low + high): 100kMi?
3. upstream Lambdas: 100kMi?
4. secondary chain tensioners: 80kMi?
5. unbalanced drafty cyl : 50kMi?

Let's see where tests clues lead...

 

Thanks, Mileage is 114K, Its a babied daily driver that rarely goes over 3K rpm. Already did prev mentioned plugs/coils/VVT sensors. Ill look up MAF cleaning, didn't see a conventional appearing one before throttle body. Is it that only small sensor that needs to be unclipped to remove air duct directly upstream from throttle body? Very small wire that doesn't travel entire interior width of intake? I can see why people would install a catch can on this engine. Not really reassuring to see oil accumulating in this area.

 

Where specifically is the MAP sensor?

 

Have you replaced the top end? Sounds like what mine was doing prior to the intake manifold replacement I just did a few weeks back (very easy job all in all). There was odd hesitation, a few misfires...then the CEL (I could turn it off, it would not come right back). My Indi knew right off that it was the intake valving (and they all break). Your car is right at that age.


https://www.fcpeuro.com/products/mer...ierburg-516475

 

> MAP vs. MAF....
The M276-NA runs with a MAP sensor located downstream to measures the intake negative PRESSURE ie. an actual vacuum.

The M276-TT runs with a MAF sensor that measure AIR FLOW charged through the intake.

Clean your oily MAP sensor with solvent or alcohol.

It's a solid state electronic unit, more or less rugged... do not blow pressure onto it !!


M276 NA Intake on driver side


The intake MAP vacuum sensor

> 5mn Cleaning Procedure:

• Unlatch connector then pull it forward
• Turn the sensor CCW 1/4-Turn down
• Pull sensor out sideway
• Clean oil /dry it out
• Reinstall /reconnect harness
• Clear ECU fault code...
• Test drive.

If that sensor was mounted facing down like Jp engines, oil would easily not accumulate inside from it's wide opening.


> Lean lag hesitations...
Next you are interested about loosing the heavy chassis throttle hesitations... This engine can run better.

-- You already have tuned-up ignition near 100kMi : sparkplugs + boots (coils).
Note: combustion misfires are not only caused by poor ignition but also drafty cyl. timings + lean mixtures penalties.

-- You noticed your M276-NA is ingesting engine oil wholesale through it's ineffective PCV system.
A lot of crankcase oil blow-by pools in the intake (TT has a seriously designed PCV that returns blown by oil into crankcase, not here!)

-- 115kMi engine is qualified for fuel delivery issues (tank filter + GDI HPFP).
Read the fuel pressures as preliminary evaluation.

-- Read LTFT Bk1+2 fuel Trims to see how the ECU rates your combustion.

Upstream Lambda exhaust sensors are overdue candidates coated with combustion carbon.

Next step is taming unbalanced cyl. blow-by losses. The stock engine is setup to develop stuck rings.

The least you can do to mitigate that is switch to a better MB-Approved PAO oil that vaporizes less at high temperatures (Motul 5W-40)
AND service oil no later than 5kMi. to preserve from engine wear...
Why ? 10kMi long oil drain stores a lot of combustion blow-by hard contaminants that are known to cause high engine wear.

Old stock "Euro polymer FS oil" has lost viscosity to become W30 lower grade.

 

Thanks guys!! I'll try that clean out on sensor (assuming MAF cleaner?). Maybe chase down a couple affordable leads if that doesnt work.The amount of maintinance this motor needs after 100K miles is a huge departure from my old W210 (240K miles only changed alternator), Build quality & longevity were why I favored this brand, Not seeing this in either form on a very well cared for vehicle. Ill follow up as I progress-- Cheers!

 

The record of M276-NA is really not bad at all.

Passed the 100K mark, the lottery is inching forward for rattling phasers.
This doesn't have to be expensive. 30mn job x2 with VVT rebuilt kits + new tensioners.

The stock vaporized blow-by can be dealt with or ignored.