So, I drive a 7.3 Excursion and re-built my injectors a year or so ago. So naturally my father-in-law signed me up to work on his 6.0 when he started to have injector issues (even though I've never touched a 6.0

Help me get his truck out of my shop!

He started having rough running / missing issues a while back. He and a buddy messed around with it but didn't get anywhere so he drove it about 350 miles home and brought it to me. I tested the FICM voltage and it checked out fine (key on and engine running). I pulled the codes and got an injector voltage code for cylinder #3. I checked the coil on #3 and it was dead (I don't recall if it was dead on the open or close side). Pulled passenger valve cover off, replaced the bad coil (tested the others and they were good) and pulled all 4 injectors on that side and refreshed them with cleaning and new o-rings. Put everything back together and it's still running rough / missing - although it appeared to run pretty well for a while (maybe 10-20 miles) before it started acting up again. Pulled codes again and getting a injector contribution code still on #3. Funny thing is, injector buzz test when cold and #4 does not click - no response. #3 clicks but it sounds a little 'weaker' than the others. Once the engine is warm, #4 will click, the others are the same???

I guess my main question is, assuming for now that the injectors are OK on that side, could he have damaged something on cylinder #3 when he drove it home with a dead injector coil on that cylinder? Would that damage, if any, now cause that injector to have contribution issues?

And any thoughts on why #4 won't click when cold but will when warm and how that fits into this problem?

Thanks in advance!