I just got this car about a month ago. Seemed to be running fine. I drove the car to PA (about a four hour drive) and began to have trouble starting the motor. It got more difficult each time I tried and finally would not start at all. It has been at a garage where the mechanics seem to be qualified, but have not been able to fix it and it has been about two weeks. They checked the fuel pump relay, TDC sensor, Air flow sensor and finally said it was the ECU. I purchased a used ECU, They installed it with no luck. Any help would be much appreciated.

Did they pull the DTC codes? IS there spark? could be a lot of things hall sensor, bad coil, but the best way is to pulled the DTC (Diagnostic Trouble Codes). Are they getting power to the coil and is there a trigger signal from the ECU?

No Spark. They said they are getting the equipment to get DTC codes today,

You stated that you started to have trouble starting the engine, but how did the engine run once you got it running?

Once started, It seemed to have a slight skip at idle, and sometimes a hesitation above around 3000 rpm.

I don't know if something getting wet might have caused the problem, but It was raining very heavy for the entire four hour trip to PA

So how did the engine run after it was started? Idleing fast, running rough or what?

You can get the Ross-Vag.com software to retrieve and reset the codes.

You can also go to the following site to find out more about DTC<ul><li><a href="http://www.sjmautotechnik.com/trouble_shooting/ecuf.html#fault">DTC Trouble codes</a></li></ul>

It seemed to have a slight skip at idle and sometimes a hestation above 3000 rpm. Also, I don't know if something getting wet may have caused the problem, but it was raining very heavy for the entire four trip to PA.
on a separate note, I really like this car! Nice power from the 20v combined with great handling and comfortable interior (this one has sport seats).

I would suspect its fuel related.
- crud in fuel pump intake screen but not likely because the 200s don't have the inner tank coating.
- fuel filter needs replacing
- dirty injectors

or
- vacuum leak
- failing temperature sensor

There is no spark

There are three sensors which can cause a no spark. Hall sensor, crank sensor and speed sensor. Crank the engine does the tach jump? If the tach doesn't jump then I would check the speed sensor. I would also check the hall sensor.

Pulling the DTC codes is the best way to determine a no spark condition. The engineers at Audi designed this for just this purpose.