hey! my escort van has got o 2.0 zetec engine fitted but its decided its not going to work anymore

ive done a few checks ive found that when i turn the engine over the plugs dont fire properly and in a weird order! also the spark is really weak! ive checked all the basics like the coil pack and tried other units but its still the same! also th injectors dont jet fuel out properly! i was wondering if anyone had any ideas that could help me! im wondering whether to get the ecu checked out?
wayne