Matt.be

2012 M278 e550.

I've had this car for several years, put an oe tune on it a couple of years back and it's been great.

It had an issue with waste gate chatter on cold start, which I got around to getting repaired recently. They had to drop the whole engine and remove the turbos to repair.

At the same time it was time for some new boots so I got some pilot sport 5s for it, seeing as traction was often an issue.

In the couple of days I've had it back from the shop I've noted that under heavy acceleration (1st and 2nd), it cuts power dramatically during the pull and not like traction control (which limits power, but doesn't cut it completely), so it jerks forward, then suddenly accerates and jerks again depending on the gear. I've also noted that the trans appears to be slipping (engine revving out during a hard pull, but not accelerating the carat the same rate).

Had a couple of thought on the issue; old tyres were 265 35 18s on the rears, theyve put 40 profiles on with the new tyres (all 4 corners), this wouldn't be tripping any speed sensors would it?

Could the Tcu be limiting the torque and cutting power now that I have good tyres and traction? Seems unlikely as its a common tune (OE tuning) and I imagine there would be a lot of complaints if this was the case.

Any other ideas?

Cheers

Matt.be

Scrap the tyre issue, I checked some photos I took of the tyre specs before and they are the same, so it ain't that issue.

S. Madman

If your traction control light is not flashing, then it's not a traction issue. Mine only does it on really cold weather or on cornering. Check your wastegates actuator for leaks. I have a video somewhere showing how wastegates shake on idle on a leaking one. Also check your logs on a pull (avoid 1-2 gears pulls unless you want to swap motor mounts frequently). Check to see if boost is hitting targets. Also check if air/fuel ratio is within spec when doing a pull.

juanmor40

Any codes?

PeterUbers

As mentioned you gotta log this -- boost, wastegate activity, IAT, etc all under WOT

Example:
https://mbworld.org/forums/w212-amg/...ge-issues.html

Matt.be

Thanks, it's just had the wastegates repaired(had the chatter) . Doesn't feel like a boost leak as its a complete cut of power very suddenly, but I'll take a look at the video you posted to be sure.

I'll do a few pulls later in the day and post some logs of the key stats here.

Matt.be

No codes unfortunately (fortunately?)

Matt.be

Thanks, interesting thread. Ill grab some logs once it stops raining.

Matt.be

Had it at the shop the last two weeks, they noted the left waste gates sticking (open) and repaired this - though I thought that didn't sound right, as its not as though power is less, feels much more like a full/electronic cut.
Drive home confirmed issue not fixed, so back to the shop it goes.

Now that I've got it back I've been able to get some logs. This is a second to third pull, foot to the floor the whole time, multiple throttle cuts during the run.
Note, boost not making it over 10 (tune takes it to 14/15) & the two violent throttle cuts.

Matt.be

And now with a 3rd- 4th pull already at 70KPH, AFR didn't read on this one unfortunately, still no codes coming up.

PeterUbers

What are your rail pressures

when were plugs and coils replaced - you may have mentioned

Matt.be

I'll do another run and take some measurements of the rail pressures.

Unsure on the plugs and coils, got the car at 60kms, has 80 on it now and I've not had to change either.

Matt.be

Incase anyone else has this issue and comes across this thread, the issue is now resolved.

It ended up being a problem with the transmission adaptive shift. This presented as a large power cut when the engine went to shift (almost like hitting the brakes and then flooring it again, before finally finding the gear and shifting).

The fix was to rest the adaptive shift and have the trans relearn the shifts. This was done by a tech, and then just required driving the car around, initial shifts are rough as it learned but get progressively smoother.

Hope this helps someone in the future.

BenzV12

I appreciate your feedback and glad you fixed the issue .
Nice to see it just that easy . It must be one of the merits of having a modern tranny
Having Driving