2002 Other Ford Models misfire, bucking, jerking under load

Hi, I have a 02 ford windstar and we drove through some standing water and the car started cutting- out and back-fired a couple of times. Then it settled down and ran ok. Later, we noticed when we were goining up hill or the passing gear kicked in, the engine would cut -out or miss intermittently causing the car to buck and jerk. To my suprise, It has set no codes. I have been expecting a misfire dtc, but nothing. I am thinking maybe the coil pack is cracked or the crank sensor was damaged. I inspected the tone wheel on the harmonic balancer, all the teeth were straight and none were missing. Any advice would be greatly apprecieted.
thanks john