2010 4.6l . Thanks

An important part of the equation is that there were no codes prior to the repairs. The head gasket, coils, injectors, plugs and timing chain were done as a preemptive because the engine was having misfire issues. After everything was done it wouldn’t start and had the p1299 code. Hit it with starting fluid and it runs fine. The misfire issues are gone, have drove about 100 miles so far flawlessly other than the no start. It never over heated or failed, and always started fine before the service. Also got a new battery, it didn’t change anything, but it was old and bad anyway. The thermostat is good, and the heat works properly as well. Air has been purged from cooling system, and it is full.