I have a 2004 Chevy Impala. v6 3.8Liter. (I use it as a Taxicab) I was driving it down the road the other day when It Hesitated, Jerked and then smoothed back out then a bout 15 seconds after that, it died! I coasted it to a side street. It would start up immediatlly every time I tried it, but then it would die after about 5 seconds. I had it towed to the Chevy Dealer. They couldnt get to it that day, and when they tried to start it the next day, it fired right up and stayed running. The Chevy Tech said he drove it around for about a half hour. No codes were found for anything. He did all the pressure tests, cadilatic converter test, you name it, he tested it. He says its a mystery to him and everybody in the shop. It has not died again, but when I feel it hestitating, I let off and ease the acceleration. It also puts off Horrible Rotten egg odors, but I thought that meant bad cadalatic converter which they say is good. Any Ideas? Thanks!