Antifreeze leak leading to coil misfire

I have an 03 Expedition. In Jan I had coil #8 replaced. A week later #7 had water in it, but was salvagable. Monday (5/24) #6 was replaced and had antifreeze in it. Apparently there is a leak, but could not be detected from the leak tracer the mechanic used. The next day it started missing while at a red light, and again when accelerating passed 50 mph. I assume it’s another injection coil, but I don’t want to replace anymore until we figure out where the anitfreeze is leaking from. There is nothing on the ground to show a leak and I do not have any white smoke coming from the exhaust. Any ideas where the leak might be?

Which engine do you have?

5.4 Liter, V8 Triton. I also checked the oil, no signs of the antifreeze getting in there.

On the 4.6L version of this engine, one of the heater hoses runs UNDER the intake manifold… A well equipped shop can pressure-test the cooling system and find the leak…

You are correct in that these coil-packs (COPS) have ZERO tolerance for getting wet…And you might as well changed the dead spark plug too…

Thanks for the info. I’ll pass it on to my mechanic.