Sounds similar to the issue I had last week and it turned out to be a dead Coil Pack.
Let the car idle and unplug one injector at a time. When you find an injector that you can unplug without changing the car's idle then you have found the cylinder with the issue. If for example, cylinder 3 isn't firing - swap coil pack 2 and 3 around. Run the same test as above. If the issue is now occurring with cylinder 2, you know it's the coil pack. If not, could be the injector.