I have a Concorde 2002, last week my car had a weird failure; started with vibration, speed slow down, smelled like burnt oil and at the end fires white smoke, the check engine light went off. Immediatly I drove to my dealer and during this time the failure had gone, so the dealer did not see it. After a week, the check engine light came on again, but without the syntoms above, now the dealer is saying that the problem is on the torque converter, what can cause the torque converter to fail? They said that the torque converter had a broken fin inside the housing.
It does sound like a t/c problem and as far as the dealer telling you a fin went bad, hmmm you cannot take a /c apart, can he see though steel, lol anyway from the indications you gave it probably is the t/c and they fail all of the time, hope this helps