envy35

Hello...New to this site!

So I purchased my A3 back in May 2014... It was one of the first recent models at the dealership. I got the car at 21 miles out of dealership, the car now has 8,900 miles on it.. close to 2 years now. I rarely drive the car a full week, because I'm provided a vehicle to get around with work, so the car is a weekend driver and just for grocery shopping. My A3 threw an EPC light back in November 20th or so of 2015, the vehicle started to shake, I was driving at about 40mph on D mode, my wife was with me in the car made her pull out the owners manual and said to get to dealer as soon as possible. Well it was the weekend and was heading to a work party, as soon as I got to the location, I shut the car off and restarted it and the light was off. Took it to the dealer mid December just the fact the dealer was super busy. When I got the car back the following day the audi tech stated possible bad fuel quality issues. Installed his G17 Additive G-001-770-A2 and said to return if light comes back on. Also the code was store and the computer stated Found Sporatic malfunctions for cylinder #3 misfire. He checked the spark plugs but found everything normal.

I wasn't fully satisfied with those answers so I took it within 2 days without appointment and car stayed over night again to have it inspected further but Audi dealer wouldn't agree to do so if code hadn't came back on again, but I insisted to check either way because I've seen other recent post similar to mine that is why im sharing my post and my issues with the vehicle on here.
So that being said, I left the dealership and drove the car often to work in the additive further more. Keep in mind i pump nothing but Chevron 91 fuel strictly ! 2 weeks later like (Jan 15) the car was at almost 60 miles left to the gallon and was driving it on D mode again at 50mph or so and the car started to rumble and steering wheel wanted to do its own thing and the light came back on. I stopped at next chevron filled the car up and restarted it and light was gone again.... Took it to the dealer this past Monday for the same issue again, I got a call from Audi later that day stating... Leaking #3 fuel injector causing carbon build up on the #3 piston causing the vehicle to set a fault for cylinder pressure too high. used scan tool and found fault P03AF cylinder pressure too high #3. removed spark ignition coil and spark plugs inspected cylinders and #3 had much carbon build up on the crown of the piston. Performed compression test and cylinders 1,2, and 4 were at 175psi , #3 was at 185psi. I was advised fuel injector #3 was going to be replaced under warranty. I got the car back today, they replaced the injector and replaced all 4 seals on them and refilled the gas tank and added 4 more cans of G17, the tech then test drove it for 50 miles under my approval and said he found the additive is breaking down the carbon as should....

Sorry for the long post, but I just can't get my head to see that, that is the actual issue... I still may think theres something else going on, like I said i read the other post before so who knows... I just wanted your guys opinion.. it would be much greatly appreciated thanks!!!