mdsooner

1993 F150, 4x4, 5.8, 199000k on it.One day it started missing. The plugs are less than 5000 miles old, wires are fairly new "not original". I did a compression test today and every cylinder was over 100 except one which was 85ish. The missing does not happen when the truck is cold but rather after a while when it is warmer or hot outside. It does not do it when the truck is cold. I just replaced the O2 sensor. Also the truck had a code of an egr valve. How do I even test an EGR valve? Any help is greatly appreciated.