I had an intermittent EPC issue so I changed my crank shaft position sensor in my 2001 A4 1.8T to see if it would fix the problem. All went well until I started it back up. It began to run very poorly and the check engine light began to flash. So I put the old sensor back in thinking that maybe the new sensor was bad but it did the exact same thing. It ran fine before other than the EPC issue about once a month. I looked to see if something else had come unplugged but couldn't find anything. The nearest dealer is far away and I havent found anyone in my town that is really good with Audi's. Any ideas?

 

So the problem was a bad vacuum leak. I guess a fitting was really brittle and when I moved my coolant reservoir I broke it. All fixed now. Except the new crank sensor did not fix my EPC issue. Still doing the same thing.