I have a 2002 A6; I have been having loud idling and violent shakes from car with check engine light on solidly; I had a tuneup done today and loud idling and a lesser violent shaking continues; Also still have check engine light on but this time it is blinking. Vehicle also does not have greatest amount of power. Vehicle has 83,000 miles and i bought it at 44,000 miles. Does anyone have an idea what i could be looking at?

 

I am betting on the coil packs.

 

Would i have to have all 6 switched or is there a specific sign when removed that tells me a specific one needs to be replaced?

 

To determine which coilpack, it is much easier to do with VAG-COM - it will count misfires on each cylinder. If you don't have access (I'm guessing you don't because you would have posted the codes), unplug the coilpacks one at a time and go for a short drive to see if it gets worse. If an unplugged one doesn't change the behavior, it is probably faulty.

If you are near Autozone they can scan for codes and then you will know what is wrong.

 

You should not drive the car with that blinking CEL!
You really need the codes read but I wouldn't want you to F yourself driving down there. Do you know anyone that has a generic OBII scanner? Avoid buying one if you can. You want to spend your money on a VAG-COM not a generic scanner.

What engine do you have?

Did you just do the plugs? Which ones were fowled?

For now if you can not get it scanned buy one coil and go cylinder to cylinder swaping it out. You don't want to blow all your cash replacing parts find the problem first.

If you have a 3.0 and the money for the coils.$160.00 total for all 6
You need to replace them all anyway cause they are crappy. But that may not be the problem, just most likely.
http://esctuning.com http://www.primepartssuperstore.com/

Even with the new ones. Go one by one so you will know which one is bad and good. That way at least you will have some used spares. Replace the plugs with them if you haven't already. Use di-electric grease on the terminals and the top of the plugs.

 

Also if your T-belt is not new pull the two front plastic covers off. (2 torx screws in each) and eyeball the belt your due for one and if that thing breaks you will loose the heads.