2004 Mitsubishi Endeavor engine rebuild:

My vehicle had no oil pressure and I had a shop to rebuild the engine. After engine was rebuilt, I drove vehicle home on a friday and it drove very well. Vehicle was parked on driveway until Sunday morning; at which time my wife drove vehicle to church(distance of 6 miles from house). When she drove vehicle back home, it was surging and running very irratically. At some point, my wife describes it as the drive light was lighted and the neutral light was blinking as she drove it home. When she started to drive it onto the driveway(slightly inclined), it barely made it onto the driveway. All the while, the " service engine soon " light was lit up. What could possibly be wrong with this vehicle? .