New to MB ownership but been a long-time BMW owner/DIYer on my e39 and e60 M5s (sold the e60 to fund the S65), so accustomed to troubleshooting odd issues. Imagining all this is correlated, but want to tap into any experience from the group before I go further down the diagnostic path. I have the full benzninja setup, so have been able to do some data review while this is ongoing.

2015 S65 with 31k miles, no engine-related fault codes.

Mx done so far:
I did a smoke test sealing off both turbo inlets and found a small leak on one IC clamp, but tightened it down - no change.
Car does have fresh motor and trans mount (they were slightly compressed relative to the new ones, but nothing crazy).
A PO had a spark plug change done at about 17k miles (but ~8 years ago).

Issue 1: it has a pretty significant idle vibration that you can feel through the seat and the steering wheel. It's irregular in intensity and pat tern (i.e., not rhythmic), but occurs all the time. Nonexistent when moving / car is above 1k rpm, but as it comes down toward idle from cold start (or even when warm sitting at a stoplight), there's an irregular vibration. I monitored "smooth running engine". Some cylinders have a wider range than others, but I don't see a standard value in the tool (probably my naivety).

Issue 2: Car feels very anemic on 2nd gear acceleration more than half the time (almost like it's NA, more exacerbated at higher rpm). Could be heat soak, but i've experienced it in cool weather (sub 70F). It's an incredibly stark difference (such that it surprises me when it actually pulls like it should). Same occasionally on a kickdown to 3rd for highway passing.

My next bets would be either a coil/plug issue given age, or a vacuum leak, but would love perspective if anyone else has faced similar issues / can recommend the best way to smoke test the vacuum system (tried from the brake booster connector, but either I have no vacuum leaks or there's a check valve I'm not seeing in the way).

TIA!

 

Commenting to follow. I’ve had the occasional vibration on start up, regardless of temp. Mine is a 16 with just under 35k miles but never had plugs changed. I suspect it is probably time to do so. Perhaps the same with yours. I do not have any acceleration issues, however, which in your case sounds like some sort of a leak. I’ve never experienced heat soak that would make me feel a change in power output.

 

Helpful to know you haven't experienced heat soak - agree that points me in the direction of a leak of some sort (could be both though at this point potentially!)

 

Check turbo pressure values, leak is first suspect.
A failing coil could be an issue as well, masked by the V12 and double spark.
Compression check would also be in order.

 

OP Lack of power after a hot soak... generally lacking power when it should be making boost that GOES.... Charge coolant pump is more than old enough to be suspect. It will pull boost at high intake air temperatures to keep it from killing itself.

Your spark plugs are more than old enough to justify replacement. Be gentle with coil connectors as old plastic likes to break easily. Buy spark plugs from MB to avoid counterfeit plugs. This really is a thing. Spark plugs require less torque when installing than I expected. Do it right. Mercedes offers a sexual lubricant to be applied to each spark plug boot before installing the coils. No dry sex!

 

Appreciate the direction here - will test the charge coolant pump/check turbo pressure values and get spark plugs in it given they're due on time at this point. Will report back once I've had a chance to get some more data over the weekend.

 

Mine is the shop today having the charge cooler pump replaced.
they ordered both OEM and the (higher flow?) CWA100 but didn’t want to install the later as it would require adapting the hoses - a project for me later as the car is tuned and will produce more heat - is on offer at FCP right now btw.

i determined it needed the pump as xentry showed high IAT and when I choose actuation for the pump it doesn’t t urn on.

It’s pretty smooth at idle (plugs just done) but it was definitely experiencing some of the acceleration issues he described, including pulling timing and falling flat above 5000 rpm.

you can also view live data with xentry (however saving it is not functional in my Benzninja setup - needs to be fixed) so you can monitor boost and IAT etc during a pull. Use a screen recording to capture.

 

Sounds like the exact same issue, will live view / screen record this weekend to confirm + run the pump actuation test.

 

The charge cooling pump in your 222 is a pulse width modulated guy. Variable speeds decided by the control unit. It can and will work intermittently before failing. Ask how I know.

 

FYI The intermittently failing charge coolant pump made for none-zero-zip-nadda codes. As far as control unit was aware everything was just peachy. It just pulled all the fun as soon as I leaned on it intermittently.

 

My pump was replaced by car still isn’t controlling IAT - shop is diagnosing relay and wiring.

the weird thing is when I try to actuate in xentry - it doesn’t show that it’s trying to turn on pump 🤔

edit: and yes this doesn’t throw codes (but does pull fun factor!) and I had to convince shop it was an issue as they just checked for codes 🙄

 

Very often the issue is air in the charge cooling circuit. PITA to bleed.