I am a g37 owner, and I bought second hand Q50 2.0t 2016 model for my wife, the car is in very good condition but there is something wrong .

when you cruise in the city it has no issue, but once you do a kickdown (full throttle) the car will downshift and the rpm will start to go up but it will stuck and the gear will not shift. Which means the speed will not be increasing much amd it will take endless time to reach 60M/H. Once the rpm reachs 7500 rpm (limit of red zone) then the gear will change. Conclusion if you accelerate normally its faster and smoother than doing kick down.

video to show you what im mean.

https://youtube.com/shorts/lOEvrNI26AI?feature=share


Any advise ? And if anyone know how i can reset the ecu, that will be helpful

 

I am a g37 owner, and I bought second hand Q50 2.0t 2016 model for my wife, the car is in very good condition but there is something wrong . when you cruise in the city it has no issue, but once you do a kickdown (full throttle) the car will downshift and the rpm will start to go up but it will stuck and the gear will not shift the rpm can reach red zone and the speed will not be increasing . Once the rpm reachs 7500 rpm (limit of red zone) then the gear will change.
video to show you what im mean. https://youtube.com/shorts/lOEvrNI26AI?feature=share Any advise ? And if anyone know how i can reset the ecu, that will be helpful

 

In your video, when you floor the pedal, the car does NOT seem to be downshifting. It appears to be holding whatever gear you are cruising in at that moment. I know that car does not have the paddle shifters, but you should be able to manually shift using the shifter stalk. Does this have any effect?

Does this happen when that car is NOT in DS mode?

Have you looked over at infinitiq50.org to see if there are any similar complaints? The powertrain in your Q50 is entirely different than in the G37 and I am sure the 7AT is using different software/ shift logic to accommodate the turbo Inline-4. Still, unless you are in manual mode, the car should still downshift at WOT.

Easiest way to reset anything is to disconnect the battery for ≈30min.

 

You are absolutely right, in the video it did not downshift, but if you do a full throttle at a higher gear it will down shift and stuck in that lower gear.

I tried to ask q50 fourms for help but no one gave me a useful information.

I checked two workshops here in Dubai, one advised me to change Transmission and the second one advised to change Transmission control unit! Which im not convinced of.

 

It is very important that you do not compare the Q to your G. They are two entirely different powertrains. The 7AT in your G37 is NOT the same as the one in 2.0L Q50. In fact, the entire powertrain for these specific (2.0L) Q cars are Mercedes sourced units (engine and trans).

You might want to consider checking some of the Mercedes forums for this issue.

I wish I had better help to offer. Perhaps others who have more knowledge will offer insight.

Edited to add: After a brief search, it appears that this transmission (the Mercedes 7G-Tronic) has a history of poor shifting behaviours. It seems that what Mercedes calls the "conductor plate" (basically the TCM) is the issue in most cases. I guess all 7AT's- regardless of manufacturer- have issues...

 

Update.Update

I visited the agency couple of days back, and the advisor said its 100% transmission issue, agency does not fix or even change the fluid, only replace the full transmission, and he advised to try to use fresh ATF fluid.

Today I completed the flush and the installation of the new ATF , I used AMSOIL flush and ATF.



The shifitng becomes much smoother than before but the car still has the issue.



Im convinced that its not transmission related since the transmission works perfectly on low RPM even at high speeds(ex.100mph).



Also i noticed today that there is no sound for the Turbo blowoff valve.



I am thinking that the issue is from the combustion itself, either fuel pump or turbo or ecu programming and the transmission is having this weird behavior at High rpm due to insufficient speed to shift and rpm is not reaching where it suppose to reach to make the shift fast enough and thats why its taking forever to change at high rpms.



Is that making any sense ?



Btw i tried today to increase the rpm while on neutral, it was also kind of slow and there is no sound for the turbo.

 

Update : problem solved.



Let me tell you the symptoms of the problem.

1- car drives perfectly as long as you dont accelerate hard. ( normal cruisng is fine, speed is not the issue only rpm)

2- once you floor the throttle the transmission will down shift and then the car will lose the power and bearly accelerate ( the acceleration will be even slower than crusing acceleration).

3- no codes or engine check light

4-no weird sounds

5- no missfires

6- idle is perfect

7- rpm is steady and engine performs perfectly on low rpm.



I disconnected the battery, removed all the intake pipes.

Clean the air mass and pressure sensor , intake pipes,



And then everything worked perfectly.



I noticed there is a very small hose connected in the back of the air filter housing, i dont remember disconnecting it, hence i belive the workshop who fixed the oil cooler forgot to connect it.



Anyway thanks alot for your help

 

Thank you for the update. I am very glad to hear that it was a relatively simple and inexpensive repair. Would you mind taking a picture of the hose that was loose? For my own curiosity, if nothing else.

Thank you, again. Enjoy the car!

 

I was going to say it sounds more Boost leak/under performance than gear kickdown.
The trans is where it needs to be however engine performance is not which is why it takes so long.
A boost leak would still let it accelerate however it would be under aspirated mode. Can you imagine a this chassis being pushed by a 150whp 2.0 4 cylinder?
Because this is what happens during a boost leak.