at one time, i had similar problems, while driving the car it jerked and almost stalled many times. one fine day, i just couldn't start the car and the injection light wouldn't go off. after 2 days, my mechanic found out that it was the flywheel sensor. it was faulty in the sense that it couldn't give out accurate readings (it goes off when being knocked, goes on again when being knocked another time). got it replaced and the car starts fine.
btw, tried the diagnostics machine but the machine couldn't find it.
thanks & happy days