Please, please help me or I'll be stranded 1000 miles from anyone I know in ANY direction. So I bought a b6 a4 3.0. Ran GREAT, had everything checked before I started my drive home, everything checked out fine. Car has high miles, but is in great condition, well taken care of. I started my drive home today, it's about a 2000 mile drive, in the middle of said drive my car began shaking pretty bad on the highway. I got the malfunction light. The car still runs, but when I accelerate it shakes very badly, barely driveable. Now for the details: The drive is practically ALL highway and so far it's all been light traffic, so no sudden starts or stops (except for the beginning of the trip to get to the highways ) At the start of my drive I fueled up with 91 octane and I fueled once more with 91 octane. Later on I was forced to put 93 octane in the car as I wasn't sure putting a fuel with less octane was safe (I only have experience with high octane cars... they run like **** when you don't put 91 or higher in them) The owner's manual did say my a4 can run on midgrade (87) but like I said, i wasn't sure that'd be ideal (I read a post on fuels and the difference so I understand now). Anyway, back to the details, I didn't hit anything or anyone, no one hit me, construction was on the road, but I haven't run over anything, and the roads weren't too terrible, I haven't had to dodge anything in the road either, so far I've have pretty good luck with roads in general. After my final fuel up about 100 or so miles, I went through a toll booth and accelerated to get past a semi that was coming out and my car began shaking and the malfunction light flashed and then turned off. My oil and tranny fluids are fine, I made sure to check them when I could stop. Later as I got back on the highway to locate a hotel, the car began shaking VERY badly and the malfunction came on and still hasn't gone off. The car starts fine and the engine sounds fine, but I'm very concerned that I won't get it to where I need to go. I have about 1000 more miles to go and I really don't want to be stranded in BFE... As I said I looked around the forums and found a detailed explanation of fuel choices and what the correct type is for my purposes, but it didn't say anything about 93 being bad for an a4. As I said before its a b6 3.0. Sorry for the novel, but I'm trying to keep from freaking out as I type this... If you need anymore details, please ask and I'll provide whatever info I can, please folks, I really need a hand here.

 

Are you getting any lights? How many miles car has? Do you know if the person that had has recently change it coils? Check for any vacuum leaks.

 

Its nothing too serious. check the coil packs and don't sweat the fuel the car can adapt between the octane

 

Here's to hoping TwinTurbo is right about the coilpacks! A little bit of dielectric grease may help out since you said your issues are only happening under load. The grease can be picked up at any auto parts store. Thats the spark part.
A fuel idea could be that you picked up some water in your gas, i didnt check before i started typing but thats a possibility if youre anywhere on the east coast with all this flooding. A worst case scenario is that your fuel pump is on it's way out, which could happen on a high milage car. not pumping out the psi under load to keep the car fueled.
Listen for sounds from the back, whining or otherwise.
Same for under the hood, any whistles like a vacuum leak like Best said.

 

Right now the only light I have on is the malfunction light. Like I said earlier everytime it comes on I get a very bad shaking and it's only under acceleration that I got the light. I'm going today to figure out what codes are being put out now, but the car has 105k miles. I don't have much of a maintenance history on this car, but I really was hoping if it was going to mess up that it'd decide to mess with me while I was still on the east coast. I'm actually in the mideast/west right now lol. How do I check the coil packs in the car? What am I looking for?

 

most likely coil packs, a very common issue. even if they have been replaced before, they might not be the "updated" pieces and still prone to failure. audi will replace them for free.

 

Well, that looks like it might be the issue, my codes are p0304 and p0343 one is the misfire code, its for cylinder 4 and the other is either cam sensor or the coil pack on that cylinder. I'm about 45 miles away from an audi dealership... will my car make it there? I can get the coil packs in today around 3 if I buy them myself.

 

To be sure of the coilpack, after codes erased, you can switch the coipack in cyl-4 with other cyl's coilpack then the code will follow to the switched cyl.

Coilpack is pretty cheap just buy & change it and additional one as spare.

The link below is for 2.7T sparkplug / coilpack but theory is same ...
http://www.audiworld.com/tech/eng82.shtml

maybe also good time to change the sparkplugs as well.