i have a 2000 discovery a plug wire came off the coilpack and ever since that happen the car will not accelerate and backfires thru the intake when you push down on the gas i have replaceced the coil pack and checked the ecu any ideas

 

You fried something but I have no idea what, start with the crank sensor.

 

No, it is not either of the crank or cam sensors.
Do a compression test, I'll bet you have a fried/carboned up exhaust valve. If need be then do a leak down test to confirm.
Let us know what your compression numbers are.