Hi, I have a 2013 GL350 Bluetec with 74,000km on it. All services done at dealership(just had service A5). Vehicle will buck/jerk while driving slow when engine is not warm(like first thing in the morning) for a couple of minutes and the RPM fluctuates vigorously. No codes are set, and it seems like a momentary power/no power situation. Vehicle operates fine otherwise.

 

Mine developed a similar sensation under light load conditions. I recorded the tech jumpingbon video, the dealer also replicated, and then uploaded some new programming g for the fuel delivery system and fixed it.

LOW ENGINE SPEED THERE IS A MISS...VERY LIGHT LOADCANT TELLAT HIGHER SPEEDS.. Cause: Correction: VERIFIED COMPLAINT. SHORT TESTED. CHECKED FOR BULLETINSNONE APPLIED.CHECKED FOR SOFTWARE UPDATES. ENGINE UP TODATE. UPDATED TRANSMISSION AND FUELPUMP CONTROL UNIT.

No more details on the invoice, though. Fixed under warranty for me.

 

My issue reappeared after a while in a bad way, just a terrible stumble feeling with the sensation of badly missing on a cylinder so that the tach needle even jumped up and down up and down while this worst bucking happened despite me maintaining very even throttle pressure. I took videos at different times of the tachometer and narrated while it was happening for the dealer. Last week, after further diagnosis and analysis of data taken during October, Mercedes concluded my EGR valve needed replacing. This work got done under warranty. After 300 miles I'm convinced, and upon reacquiring the truck immediately felt, that my vehicle now responds to throttle input in a much more linear and smooth, very predictable manner. It feels like it should now, whereas before throttle input was not necessarily met by the most smooth responses at takeoff and very low speed. In fact, most often the first response in the morning was a single stumble or miss and then sometimes that happened repeatedly during warm engine driving on a level road at low speeds, as described.
for the record, the exhaust gas recirculation or EGR valve device replacement seems to have addressed this problem for me. I hope it holds, but if it's the true replacement of a defective part then it should very well do so. If the old EGR valve was not behaving properly, then the engine was not able to perform as intended if trying to adjust or somehow compensate or manage for a bad mixture or less than optimum conditions. Oddly, I never got a check engine light or codes during all this time. I'd love to think my MPG will improve, but that does not appear to be the case.
This gives me a chance to remind everybody that the dash computer readout that calculates MPG overestimates the figure, at least 8 percent every time for me, so do your own math.

 

Where is this video you mentioned?

Here's the part number and price for future references.
https://www.mboemparts.com/oem-parts...PWxheWVyXzE%3D

 

I took videos on my phone and sent it to the service advisor at the dealership, what do you mean where is it? The point is rather than just describe the symptoms, I was able to document then happening on several occasions and proved it to the dealership and Mercedes. The point is not for you to see the video, it just shows the IP with the tach needle bouncing rapidly as I drive to maintain a steady slow speed under very low load condition with a steady pedal.

 

I thought maybe there was a video for all to see, no big deal.

 

Had the same issue with my ML350 Bluetec when it was 3 days old. I went back and forth with the dealer for the next 5 weeks and eventually they replaced the exhaust which fixed the issue. Don't know why they had to replace the complete exhaust system because I think the issue was caused by faulty sensors that sit in the exhaust system. I've read a post from another person who had the same issue with those sensors.