Fang88

I ran into a serious problem on my road trip this past weekend. While I was accelerating on the freeway, the car suddenly stopped accelerating and I guess the closest description of what happened is as if the motor kept choking out. I had to pull-over and restart the motor and the problem persisted again! It kept happening while accelerating from 45-65 and in 4th and 5th gear at least over 20 times over the road trip. At first, it freaked me out as it was a huge safety hazard but I had no choice but to keep driving as I was in the middle of nowhere. I literally had to feather the throttle super lightly for the rest of the road trip all the while not knowing if the car was going to completely break down on me. I had to suffer over 8 hours of driving not knowing if the car would breakdown.

Took the car into service on Monday and just got a call back. Service department is claiming they couldn't find the issue, they reprogrammed the car and test drove it and it's fine. I'm almost sure this problem hasn't been fixed and worst part is that the problem will probably happen the next time I go on a road trip. Super frustrated right now...going into the service dep. my main concern is that they wouldn't be able to mimic the acceleration issue on command.


Car is at 6k miles.

CorradoJr

Did the engine die, and you havd to restart it? Or, it felt sluggish as if it was sputtering and once you backed off the accelerator it regained composure? Or, in order to "reset" things, you physically turned off and restarted the engine?

Were you using the shift paddles? And perhaps something was stuck under the accelerator pedal? Just my initial observation.

Fang88

The engine did not die, nor did any warning lights turn on. You described it perfectly, it felt sluggish as if it was sputtering and if i backed off the gas pedal it would regain composure. (Keep in mind that backing off the gas pedal and having the car slow down 10-15mph on the freeway is quite dangerous especially if you're in the fast lane). I figured that out after pulling over the first couple of times.

I was not using the shift paddles. I thought maybe it had something to do with the auto-braking driver assist feature malfunctioning(was on almost empty road with no traffic) and i turned that off, but problem still persisted. Issue happened in comfort and sports mode.

miketc

Fang, did you refill along the way, bad gas may also cause this.

Fang88

Filled up at Shell prior to roadtrip and in the middle, only put 91 (highest there is in cali).

CorradoJr

I don't have a W205, so I'm not sure how "stiff" the kickdown point is on the accelerator pedal. On older MB's, it was noticable.

Fang, are you certain you weren't experiencing the kickdown position on the accelerator? Did you "floor it" with some gusto?

Fang88

Definitely didn't floor it. The problem would happen pretty early maybe approximately at 40-60% into the gas pedal max travel length. I was literally pressing down maybe 5% of the pedal for the rest of the trip...it was a nightmare. If it's something as simple as a fuel issue, i'll try switching gas for the next few fill-ups and see if it happens still.

CorradoJr

Does this video more or less describe your situation?

This guy's kickdown isn't working, and the car is slowly losing speed on the highway. Different car/technology, but same principle.

Fang88

That looks exactly like what was happening to me. Of course, a lot more vulgar language was involved in my instance.
I should probably show my service advisor this thread...

CorradoJr

I'd say in my opinion it seems to be a transmission issue. Maybe your dealer can try checking again or reflashing.

Try a few other things to see if you can narrow it down. Does it happen at a certain speed, when car is cold (not warmed up), etc. to help with the diagnosis if possible.

In the meantime, if it happens again, you can use the paddle shifter to request a downshift, which may override things.

Fang88

@CorradoJr - Thank you, really appreciate your advice. Going to get my car back today to see if it still happens. If it does, looks like another service trip will be necessary.

CorradoJr

Glad to help! We are all here to help each other enjoy the W205 and conversations surrounding this great car.

Hope it gets fixed and goes away for good!

Fang88

Very curious if i'm the only person who has experienced this issue with the W205. Maybe this thread will answer some questions for someone in the future.

Nkubath

i had a similar problem. sadly this isn't a cheap fix. you will have to take it to Mercedes and get it looked. I'm guessing they will need to put a new accelerator pedal cause thats what mine needed. hope this helps

Dramz

i had the similar issue this weekend near Calgary from Edmonton to Banff the only difference is that it happened after i had stopped at services ( parked the car in parking ) and then went back on the highway i started the rev going up and the response was like dragging( as if the parking break was engaged /but no sign on the dashboard ) and the temperature gauge showed 100, stopped the car once was safe got the hood up and felt the hot engine fumes that you would smell when engine overheats . i got the Mercedes Road side assistance and got the car towed to local dearlership in Calgary . Used the trip interruption program , dealer checked the car in two days time and said no error/messages in the car road test fine + added that it could be a safety mechanism in place. the car has been driven 400 km stretch before without any issue , have the original dealership in Edmonton have a look at it. Hopefully they can provide an answer.

Fang88

Just a quick-update. Still have issues with the kick-down. I can't pinpoint exact speed and gear as it seems to happen in a wide range. Good part is that issue is singled out now so I've learned to adjust to the problem when it happens...even though it shouldn't be happening in the first place. Thinking about taking it into dealership again. Car is fully under warranty.

mercuk

Fang88
I had a similar problem last week. C220 sport manual
Engine slowed down from 70mph to a crawl, kept changing down gear but the engine just got more sluggish. It felt like the brakes were applied, no handbrake light though and no energy management light.
Pulled over and restarted the engine and it seemed to drive fine afterwards. No problems since but I have booked it into the dealer this Friday, will let you know what they say

Fang88

Ugh, it seems like this is starting to reveal itself as a pretty common issue! I suggest you tell them you suspect it's the kick-down accelerator. Most likely issue won't show up when they hook-up to computer nor will they be able to mimic it on command. I wish there was some other way for them to diagnose the issue...

Glyn M Ruck

This is obviously not a winter fuel vapourisation issue as it's happened with multiple tanks of fuel.

What it might be is a transmission temperature or temperature sensor related issue. When the transmission temp sensor detects a rise in fluid temperature above preset limits it causes the transmission to change down & increase engine revs & thus circulate more fluid via the cooler (transmission pump is input shaft driven) & reduces power until normal temperature operation is attained.

The temp sensor might be faulty or the TCU programming over sensitive.

mercuk

Glyn M Ruck
Interesting if temperature is the cause, would there have been an indication on the dashboard? I can't remember seeing any warning lights, but I was concentrating on getting out of the fast lane to the hard shoulder in peak traffic!

Fang88
The kick-down accelerator issue would only be for the automatic model wouldn't it, mine is manual?

BlackjackM

On my C204 every once in a while it would go into a limp mode if it detected turbo PSI overrun (for instance, pulling into traffic quickly in the rain and spinning the tires a bit). I would get a check engine light and limp mode but everything was fine once I turned it off the back on again. Wonder if this is the same issue. Only happened to me a couple of times.

Glyn M Ruck

This applies to Auto.

There would be zero dash indication. The ECU/TCU just handles it!.

Glyn M Ruck

If it happens spinning the wheels it is an ESP reaction to breaking traction.

ddeliber

Speaking of ESP, this sounds like what would happen if there was a false positive on breaking traction. Should be easy to verify - just turn off traction control and see if it happens.

BlackjackM

No, it wasn't. The wheels spun for a brief moment (RWD), the check engine light came on and the car went into limp mode- the turbo was essentially shut off. I had to turn off the car and restart and everything was fine.