snowpooch

Driven turbo cars for the past 7 years, so don't notice the lag being anything remarkable, perhaps I made adjustments along the way

peacemf

so this only happens with the diesel engines or petrol too?

ive got it on my x5
worrying when you just want to go, or when you have an chance to go at a junction, but you have to go quick before being rammed by a car!

sydunipete

I recently had some success after nearly 3 years of trying to fix this problem on my (petrol) 2006 ML500. My dealer upgraded the software in the engine management unit and the lag (and subsequent surge) has gone away.

Touch wood ... this is a long term fix. In the past reseting the adaptive learning in the transmission resolved the issue, but the lag/surge would return within a few weeks. But this has been 2 weeks now with a lot of kilometers travelled so I'm starting to hope a solution has been found.

lkchris

There's a DTB (dealer technical bulletin) to fix this now. For diesels only.

DTB S-B-27.00/104 "Slow Acceleration with Gas Pedal Hesitation"

DUTCH

Thanks Kent!

NickIndy

Uh yeah...almost had to change my shorts a few times. You learn quick not to pull out in front of people. Once it's ready to move it really moves, you just don't know when it's ready.

robalo220

I have an 07 ML 320 CDI also and the lag is more noticable when cold. Less so when it is warm. This would lend to being more turbo lag as stated by a previous poster that the exhaust gasses aren't warm yet and don't provide as much boost when cold. Still present when warm, but you learn how to accelerate. I usually just go light on the accelerator first until it starts to roll, then floor it and it will throw your head back.

ima55r2

Exhaust gas temperature doesn’t matter since it only spins the turbine. The compressor works with the incoming fresh air. Turbos actually work better in cooler weather...condensed air molecules.

lkchris

Blah, blah--the fix is updated transmission software as posted.

DUTCH

I'm scheduled to have this done on this coming Wednesday. I'll let you all know if it fixes it.

lkchris

I haven't decided yet if it fixed mine, but I haven't experienced the old problem either. Just not sure I've created the conditions that creates it.

dgiturbo

Printed this fix out and gave to my dealer to complete. They read it, and did nothing as they had no idea or knowledge of it. Said they will get back to me once they researched it? Oh well. Need to find another dealer. Or maybe they are waiting for my warranty to run out...
Anyway, car runs great and so far the lag has completely gone away. Maybe due to it being Summer?

DUTCH

Need to find another dealer for sure. The DTB says to flash the transmission with a version later than February 08. What kind of dealer can't understand that?!??!!

DUTCH

Had the DTB done yesterday; and I can see only a miniscule, if any, improvement in the acceleration lag. I also ended up with an even harder 2->1 downshift out of the deal.

There is new software in the works to fix the hard 2->1 downshift in all 722.9 transmissions on the 642 motor. It's already been released for all models except the 164 and the 251. That part of the new software is to be available later this Summer or early Fall.

In the mean time there is a new ATF 4134 (spec 236.14) P/N: 001-989-68-03-10 that is being recommended for all 722.9 transmissions. It it is supposed to run cooler, which might be a help for that hard 2->1 downshift; since on mine, it always seems to be worse when the weather and engine/transmission are hotter.

Price on the old ATF 3353 (spec 236.12) was/is $15.00/liter. The new ATF 4134 (spec 236.14) is priced at $32.50/liter. Ouch!

I'm scheduled to change to it and a new filter (40,000 miles on the truck) next week Wednesday. I'll let you know if I see any improvement.

DUTCH

Changed filter and ATF to the newest ATF 4134 this morning at my Indie's shop. We only did a single drain and refill (at $37/liter X 6), so it's now about half and half. It's really too early to tell for sure, but it does appear to shift much smoother. (Placebo effect?) Time will tell.

The refill procedure is a very serious pita; and I am curious as to how the dealers can even properly follow the WIS instructions. There is a stand pipe inside the pan clipped on the drain plug. You add back 1 liter more than you drained with a special adapter through the drain plug. Then run the engine/tranny and move through P-R-N-D a few times.

With the engine idling in Park and the STAR Diagnosis System connected to measure the internal transmission temperature, you allow anything that will drain out over the stand pipe at 40°C. There is a very strong warning that, if the temperature is above 40°C, too much will drain out.

The big problem is that the transmission temperature scoots right past 40°C when you're moving it through the gears; and it ends up at about 68°C. There's no way to stop the temperature rise. How do you know when to stop it from draining at that temperature so that you don't drain out too much!?!! We guessed. Hopefully, it's close enough. It does seem to drive OK.

Engineers! Arrgghhh!!!!

bearded8

I nearly got broadsided by a truck recently when my '06 E320 CDI just sat still and quiet for about three seconds before launching into a left turn (in front of the, by then, right-on-top-of-me truck). I had complained to my dealership service department about the same problem while moving, and was told it's "the nature of the vehicle." This was the first time I experienced it from a dead stop, and like others have said, it's SCARY. I'm glad to read the service bulletin on "slow acceleration," but it looks like it only addresses the problem if it does "NOT occur when the accelerator pedal is depressed into the 'kick down' range..." Mine is worst when I floor it. And I'm always in sport mode, so I should be in first gear from a dead stop. I'll take the bulletin to my dealership though and ask again. Thanks for posting.

BTW: My '07 CLS550 used to shudder and refuse to downshift when I kicked it to pass at speed. They never did get that fixed.