I've noticed this problem from some of the other Audi enthusiast sites.

Som mentioned that it's from lower octane gas being put in on the Q. In Canada, only these gas stations are listed as top-tier:
Chevron, Esso, Petro Canada, Shell and Sunoco.

In Alberta, Husky Gas stations carry a 94 octane but it is not listed in the top-tier gas.

I'm just curious, what brand of fuel do you use on your Q?

 

shell v-power

 

Used Shell-v-power exclusively. Then all six injectors went at the same time. Dealership said it was from "bad fuel quality" I told him nothing but Shell in the tank. Dealership gives me stunned look.
Since then I fuel up at Costco and use Audi Injector cleaner........run's like a top!

 

do you just buy the injector cleaner from the dealership?

 

yes and it's not that costly.

 

What brand injector cleaner does Audi use? I am just wondering if other places other than dealer sells them.

 

Their own Audi brand.

 

Today, I took my 2010 Q5 in for 55000 service. the delaer called me back and said that they need to keep the car for few days due to carbon build up. They have to take the engine apart . I did not have any sympton, other than once in a while when I started the car, it stalled. Is this normal. What problem would it cause due to carbon build up. Your help is apperciated as the dealer did not provide me with much info.

 

Not sure about the carbon buildup but injectors have been a problem. Fuel quality is a supposed issue as well.

 

I had 4 out of 6 fuel injectors replaced at about 11000Km and I always gas up at Shell using V power. It obviously did not help.