1995 Dodge Avenger Why the car will not stay started when d

I have owned this 1995 Dodge Avenger for at least 4 years. The car was given to me by a relative who owned it for a few years. The car was given it's routine maintenance ( tune up, oil changes, etc.) For the past 4 yrs, and just had it's tune up & oil change a few weeks before it started doing the following: I was leaving for work one day and upon turning the key, I heard a sound like a backfire(popping), but the car still kept running. Once I but the car in Drive, and drove for at least 9 blocks, the car went dead, shut down completely! I thought the car had overheated, so I waited for awhile, the car started right up, but I was only able to drive for a few blocks. I have had the distributor changed and a crankshaft sensor, but still not running. The mechanic sas that the car does not have any "fire". What can we do next?