'Check engine light on

That one is hard to say, but always replace all plugs and coils not just the individual one that was failing first. re check the code again and see whats coming up.

It's a good idea to perform a cylinder compression check, make sure the engine is sound. Also, you can swap #1 and #3 fule injectors, erase the DTC, see if the code comes back to #3 or #1 cylinder, if moves then the injector is bad. You can always try this with ignition coils and plugs too.