Ernest Gann in "Fate is the Hunter" described one event in which he
lost nearly all power on 3 of 4 out of LGA once, and another time that
all 4 quit simultaneously with a load of passengers over the Pacific.
The first event was caused by the mechanics testing a new type of
spark plug, which they "unfortunately" had time to install on 3
engines. The second was a glitch in the fuel system.