Unfortunately my first post has to be one about an issue.

I bought a 2007 A4 2.0T from Carmax on Friday (11/16). Tonight I started it up at a friends house and went out. To show off a little I slipped it into S mode and accelerated pretty hard. Right as I was naturally letting off (around 40 mph), a light (I'm not sure if it's a tranny or CEL) started flashing on the dash and all was well for a few seconds. When I went to accelerate again, acceleration was extremely rough/jerky. So I immediately turned around and parked it again.

On the drive home I noticed some odd things: the roughness or jerking or bucking is most severe at lower RPMs (between 1,100 and 1,800). At 2,000-2,700 it is just very fast so it seems to be not as intense. Above 2,800 or so it almost seems non existent but there is an obvious lack in acceleration that I'd usually feel at that RPM. Also, in Neutral there is no issues at all, it is only when the car is in reverse or drive, it also occurs in S mode and in manual shift mode. During the drive the light alternated from flashing to steady, mostly being steady. Also, during engine deceleration there is no stutter or jerking (even upto as high as 3k RPM). Also the idle is slightly rougher than usual, and at a slightly lower RPM (even in neutral, yet revving in neutral displays no ill-symptoms).

I have a 30-day warranty just from the purchase, and a 6 year or 100,000 mile warranty on it. Unfortunately this happened the night before Thanksgiving so I won't be able to get it in until Friday. I'm wondering if you guys could point me in a direction so I can lead the CarMax people that way. This is my very first car I purchased myself and I've never dealt with warranties or anything. Will I be getting a loaner to use for work in the meant-time, how does it all work? I'm extremely mad at myself that I broke the car this soon so excuse my rambling and many questions.

 

Update: The light that is coming on seems to be the "Malfunction Indicator Lamp" according to my owner's manual.

 

Your engine is misfiring.

 

Any idea what may be causing that? I did put in Chevron Premium yesterday as well, I filled it up from a quarter tank from whatever gas the dealership had in it. Which I believe was regular because the car ran better after I put the premium in, is mixing it like that bad? Other people I've talked to seem to think it could be a misfire issue due to an injector or something along those lines.

 

Shop called me earlier today. Misfire on cylinder 3 due to a faulty coil. However, the coil had some coolant residue on it and they're keeping it over the weekend to figure out the source of said residue. Hopefully this doesn't open up a can of worms on their "152 point inspected" vehicle.