What is the proper gap for a 2001 F150 5.4 L Triton

The proper gap is .052 - .056 inches. Make sure you use Ford / Motorcraft plugs and coils! Very important. Aftermarket coils do not work well on these vehicles.

“Better While in park put in drive and it won’t stay on” Highly recommend scan testing - while replacement of coils and spark plugs may be in order - that isn’t likely to cause engine to stall.