I just recently bought a 2000 A6 2.7t. It is automatic if it matters any with the problem at hand. I am having a check engine light on due to a misfire on cylinder 4. I changed all the plugs due to not knowing the last time they were changed. I also changed the coil pack to cylinder 4. Started the car and still misfire on cylinder 4. Cleared code and still comes back. Switched coils around thinking that i got a bad coil. but nothing changed still misfire on cylinder 4. I tried unplugging the injector to cylinder 4 thinking that it was sticking wide open, and nothing changed. I unpluged the coil pack while car was running and didnt notice anything different. Car still idles rough enough to shake car at idle. could it possibly be the ICM on top of the air filter box? their are two differnt ones on top of the box. One with black connectors and one with brown connectors. Is their one for each side of the motor? Is their any way to test the ICM to either rule them out or pinpoint it? or should i go back to the idea of a possible stuck injector. The car has 123000 miles on it. the timing belt was just done at 90000 miles. Or is their any other common issues to look at for cylinder 4 misfire.

 

On my car I was able to swap the "power output stages" (POS) (aka ingition control module, igniters, ect) by just moving the wires a bit. Make sure each module has the same color plugs on each end. If your problem goes to "misfire #1", you have found your problem. Modules are about $200 but there are some that can be "made to work" for about $100. (I have an "extra" one that will give misfire on #2 or #5...)

 

got it fixed. It was the ignition control module that is located on top of the air filter box

 

When you got the check engine light, what codes did it show for that problem.