The Audi A4 2.0 is generally a very reliable engine. They have had some problems with their high pressure fuel pumps and the associated camshaft drive lobe, but the motors themselves, like their 1.8l predecessors are pretty reliable. This particular engine was over reved and broke a rocker arm and dropped a valve down into the cylinder. The cost to rebuild the engine so we found a used Audi A4 2.0 engine to replace the existing one. We don't often use used parts, but it was the only way to economically keep this car on the road. As is typical with used engine swaps, we had to transfer some of the parts from the current engine because they were broken or missing on the "new" engine. We also found after the engine was installed that a couple of the sensors and the wiring harness for the replacement engine were defective. These of course would have been easier to replace on the engine stand, but there is no way to test them until we have the engine in the car and running. These sorts of variables with used parts can make the cost harder to pin down until the project is complete. We always try to be upfront about these potential cost variables and make sure we tell the customer to expect a few hundred dollars worth of additional expenses for this extensive Audi Repair.