Mihai Alexandru

Hello,
I have a 14' GLK 220d with 4 matic and the 7 speed transmission. Car had around 350k km (217k miles) couple months ago when I changed the timing chain, the transmission oil and other things like bar links, tie rods, ball joints, control arms etc, but those are not related to the problem. The transmission oil was the original one, never changed it. The car sat disassembled for almost 2 months as the mechanic had some health problems (it was a local service garage). After it was done I took the car and everything seemed fine. He told me the car could fell sluggish, but that it would get back to normal shortly. The car ran normal but, after a week or so, while on the highway doing 140kmh (87mph) the car suddenly started slowing down and the accelerator did little to nothing. No lights came on, nor fault codes as I checked with 2 different scan tools from 2 different mechanics. That power loss would happen for around 1 minute. At first it happened at roughly 400-500km (250-300 miles), but now it seems more randomly, as sometimes its very frequent (happened twice on the motorway in less that 5 minutes) and other times very rare (did 1700km (1000 miles) without it occuring). I thought it may be related to the injectors or the DPF, so I used 2 or 3 injector cleaner additives and one for the DPF, although I knew the DPF was clean because it was sent at a cleaning service while the car was disassembled (and even the guys there said it was clean) and also the diagnose tool showed 0 ash and 9.7g of soot. Even if I am doing 145kmh on cruise control, the car would just start to slow down. If I press the gas all the way down, it shifts to fifth and starts to accelerate very slowly, but it cant get past 130kph. I am afraid it may be due tot the transmission oil as I read online that changing it after so much time could make it slip gears, but the gearbox seems to shift just fine. Even when the power loss occurs, I dont think it slips through the rmp range, it just revs if I floor it. And its not happening only at motorway speeds, I think it happened even at 70-80 kmh (45mph), but never in town, only on outer roads. The 2 mechanics I have been at are clueless since there are no lights or error codes. Does anyone have any idea or may have encountered something similar?

Mmr1

I have no idea. A failing fuel pump? Or Turbo issue. If you drove it with the scanner hooked up could you monitor fuel and other parameters?

Mihai Alexandru

I didnt think that anything failed since everything was fine before, but it might be just a coincidence nonetheless. I will tell my mechanic about the parameters. He drove it with the scanner, but looked only for error codes I think. Do you reckon the parameters will look odd even when the car is running fine or only when the power loss occurs?

Mmr1

Yes something goes off. The question is what.

Mmr1

Maybe a failing fuel injector or what controls it or wiring . It should be traceable while driving

Mihai Alexandru

Dont know if this can be related, but when the power loss first happened I brought the car back to the mechanic and he said that he coded 2 of the injector codes interchanged. He entered them in the right order, but the problem as stated persisted. I will look into the live data while driving, see if there is anything out of place and post an update. Thanks for the advice!

Mbcarver

I'm having this EXACT same issue. I've checked the intercooler hoses for leaks, that's a common first thing to check. It's a complete mystery to me. Zero codes or check engine lights.

Mihai Alexandru

Have you changed your transmission oil according to the manual? Because if you did so, I can rule out the possibility of a faulty transmission due to the old oil being changed so late.

Mbcarver

Yes, it's definitely not transmission. It's shifting fine. It just feels like no boost is being made. If I had to guess, it's going into limp mode for some reason. But with no engine codes, I'm not even sure of that.

Mihai Alexandru

Did it start happening to you suddenly? Because it happened to my car right after I had the timing chain changed and I thought that the mechanic put it back together wrong or something.

Mbcarver

It's been happening every so often ever since I purchased the car around 25k miles ago. So it's very possible that it's something related to a vacuum or boost leak or something not put together correctly. However, those things generally will either throw a code or will happen consistently.

Mihai Alexandru

Thanks for the feedback! You're the only person that I know that has the same issue. Since it's not showing any light or code, I'm afraid even with a scanner it might not be really traceable, unless you're looking at the tool right when it's happening. At least now I have peace of mind that it's not the trans. I hope it's as simple as just a few loose lines or hoses. Is your car also the 2.2 diesel?

Mbcarver

Correct, I've got a 2014 GLK250 w/ the 2.1L turbodiesel. I've seen a few people with modern Mercedes diesels (sprinter vans, mostly) with similar issues. But I haven't found a case that solves my issues.

andreigbs

Just confirming: you guys have BOTH checked your driver side intercooler boost hose, correct? Most times if you have a very small tear, it won't leak until a certain pressure is reached. That's when the ECU will realize there's an underboost situation and pull boost, or go straight into limp mode to protect itself. Of course, if in limp mode you'd definitely have CEL on and code(s) in memory. Unless yours has been "tuned" and it ignores low-boost errors (ask me how I know).

Mbcarver

Yes, I mentioned it several comments above: "I'm having this EXACT same issue. I've checked the intercooler hoses for leaks, that's a common first thing to check. It's a complete mystery to me. Zero codes or check engine lights."

Mihai Alexandru

I'm not in town right now, but I'll have a look at it in the weekend. It might be pulling boost, but it's strange that it sometimes doesnt happend for very long periods. I dont thinks it goes into limp mode since there is no CEL on or any other light, nor any codes. The car has not been tuned since I am the original owner. Thanks for the heads-up, I'm going to check the hoses for tears and proper connection.

Mihai Alexandru

I'm from Europe and we tend to round up engines sizes . I'm looking forward to any updates if you eventually sort it out. Best of luck!

MBKLUE

Thread Hijack...


You have a GLK 220d and a GLC 220d? I'm sure some folks here would be very keen to know your impressions of both and comparisons, which you prefer etc. But, on a new separate posting so we're not getting off topic here.

Multumesc